High-frequency signal line and manufacturing method thereof

ABSTRACT

In a high frequency signal line, a first signal line extends along a first dielectric element assembly, a first reference ground conductor extends along the first signal line, a second signal line is provided in or on the second dielectric element assembly and extends along the second dielectric element assembly, a second reference ground conductor is provided in or on the second dielectric element assembly and extends along the second signal line. A portion of a bottom surface at an end of the first dielectric element assembly and a portion of the top surface at an end of the second dielectric element assembly are joined together such that a joint portion of the first and second dielectric element assemblies includes a corner. The second signal line and the first signal line are electrically coupled together. The first and second reference ground conductors are electrically coupled together.

This application is based on Japanese Patent Application No. 2012-240091filed on Oct. 31, 2012, International Application No. PCT/JP2013/070723filed on Jul. 31, 2013, and International Application No.PCT/JP2013/073639 filed on Sep. 3, 2013, the entire contents of each ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to high-frequency signal lines andmanufacturing methods thereof, more particularly to high-frequencysignal lines preferably for use in transmission of high-frequencysignals and manufacturing methods thereof.

2. Description of the Related Art

One known example of an invention relating to the conventionalhigh-frequency signal lines is a high-frequency signal line disclosed inJapanese Patent Laid-Open Publication No. 2011-071403. This signal lineincludes a main body, a signal line, and two ground conductors. The mainbody is formed by laminating a plurality of insulating sheets which aremade of a flexible material and linearly extending in a predetermineddirection. The signal line is a linear conductor provided on theinsulating sheets. The two ground conductors are provided on theinsulating sheets. The signal line is provided between the two groundconductors in terms of the direction of the lamination. With thisarrangement, the signal line and the two ground conductors form astripline structure. The high-frequency signal line is used for, forexample, connection of two circuit boards included in an electronicdevice.

In manufacturing the above-described signal line, a signal line and twoground conductors are formed on a plurality of large-sized motherinsulating sheets, and the plurality of mother insulating sheets arelaminated such that the signal line is provided between the two groundconductors, such that a mother laminate is formed. Then, the motherlaminate is stamped (cut) out, such that a plurality of signal lines aresimultaneously manufactured. To obtain a larger number of signal linesfrom a single mother laminate, a plurality of signal lines are arrangedin a matrix over the mother laminate with the gap between adjacentsignal lines being as small as possible.

For convenience of the layout of circuit boards, a battery pack, aliquid crystal panel, etc., inside electronic devices, it is preferredin some cases that the signal line disclosed in Japanese PatentLaid-Open Publication No. 2011-071403 has a bent configuration, such asL-shape or U-shape, when viewed in plan in the direction of thelamination. When such bent signal lines are arranged over the motherlaminate, the gap between adjacent signal lines is large as comparedwith a case where linear signal lines are arranged over the motherlaminate. Accordingly, the number of signal lines obtained from a singlemother laminate decreases, and the manufacturing cost of the signallines increases.

SUMMARY OF THE INVENTION

In view of the foregoing, preferred embodiments of the present inventionreduce the manufacturing cost of a high-frequency signal line which hasa bent configuration.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a high-frequency signal lineaccording to a preferred embodiment of the present invention.

FIG. 2 is an exploded perspective view of the high-frequency signal lineof FIG. 1.

FIG. 3 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 4 is an exploded perspective view of the signal line portion of thehigh-frequency signal line.

FIG. 5 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 6 is an exploded perspective view of the signal line portion of thehigh-frequency signal line.

FIG. 7 is a cross-sectional structure view of the high-frequency signalline of FIG. 1 taken along line A-A.

FIG. 8 is an external perspective view of a connector of thehigh-frequency signal line.

FIG. 9 is a cross-sectional structure view of the connector of thehigh-frequency signal line.

FIG. 10 is a perspective view of an electronic device including thehigh-frequency signal line.

FIG. 11 is a plan view of a mother laminate.

FIG. 12 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 13 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 14 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 15 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 16 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 17 is a plan view of a mother laminate in manufacture of adielectric element assembly of a high-frequency signal line according toa comparative example.

FIG. 18 is a cross-sectional view of a high-frequency signal line in astep of compression bonding.

FIG. 19 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 20 is a cross-sectional view of the high-frequency signal line in astep of compression bonding.

FIG. 21 is a plan view of a high-frequency signal line according to thefirst modification when viewed in plan in the z-axis direction.

FIG. 22 is a plan view of a mother laminate.

FIG. 23 is a plan view of a mother laminate.

FIG. 24 is an exploded perspective view of a signal line portion of ahigh-frequency signal line.

FIG. 25 is a cross-sectional structure view of the high-frequency signalline taken along line A-A.

FIG. 26 is an exploded perspective view of signal line portions of ahigh-frequency signal line according to the third modification.

FIG. 27 is an exploded perspective view of a signal line portion of thehigh-frequency signal line.

FIG. 28 is an exploded perspective view of another signal line portionof the high-frequency signal line.

FIG. 29 is a cross-sectional structure view of a joint portion of asignal line portion and another signal line portion of thehigh-frequency signal line.

FIG. 30 is an exploded view of a signal line portion of a high-frequencysignal line.

FIG. 31 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 32 is an external perspective view of a high-frequency signal lineaccording to a fifth modification of a preferred embodiment of thepresent invention.

FIG. 33A is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 33B is a cross-sectional structure view of the signal line portionof the high-frequency signal line.

FIG. 34 is a plan view of an end of the signal line portion on thenegative side in the x-axis direction.

FIG. 35A is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 35B is a cross-sectional structure view of the signal line portionof the high-frequency signal line.

FIG. 36 is a plan view of an end of the signal line portion on thenegative side in the y-axis direction.

FIG. 37 is a cross-sectional structure view of the high-frequency signalline of FIG. 32 taken along line A-A.

FIG. 38 is a perspective view of an electronic device including ahigh-frequency signal line.

FIG. 39 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 40 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 41 is an exploded view of a signal line portion of a high-frequencysignal line.

FIG. 42 is a cross-sectional structure view of the signal line portionof the high-frequency signal line.

FIG. 43 is a plan view of an end of the signal line portion on thenegative side in the x-axis direction.

FIG. 44 is an exploded view of a signal line portion of thehigh-frequency signal line.

FIG. 45 is a cross-sectional structure view of the signal line portionof the high-frequency signal line.

FIG. 46 is a plan view of an end of the signal line portion on thenegative side in the y-axis direction.

FIG. 47 is a cross-sectional structure view of the high-frequency signalline of FIG. 32 taken along line A-A.

FIG. 48 is an exploded view of a signal line portion of a high-frequencysignal line.

FIG. 49 is an exploded view of a signal line portion of thehigh-frequency signal line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, high-frequency signal lines and manufacturing methodsthereof according to various preferred embodiments of the presentinvention will be described with reference to the drawings.

A configuration of the high-frequency signal line according to apreferred embodiment of the present invention will be described belowwith reference to the drawings. FIG. 1 is an external perspective viewof a high-frequency signal line 10 according to a preferred embodimentof the present invention. FIG. 2 is an exploded perspective view of thehigh-frequency signal line 10 of FIG. 1. FIG. 3 is an exploded view of asignal line portion 10-1 of the high-frequency signal line 10. FIG. 4 isan exploded perspective view of the signal line portion 10-1 of thehigh-frequency signal line 10. FIG. 5 is an exploded view of a signalline portion 10-2 of the high-frequency signal line 10. FIG. 6 is anexploded perspective view of the signal line portion 10-2 of thehigh-frequency signal line 10. FIG. 7 is a cross-sectional structureview of the high-frequency signal line 10 of FIG. 1 taken along lineA-A. In the following sections, the direction of the lamination of thehigh-frequency signal line 10 is defined as z-axis direction. Thelongitudinal direction of the high-frequency signal line 10 is definedas x-axis direction, and the direction perpendicular to the x-axisdirection and to the z-axis direction is defined as y-axis direction.

The high-frequency signal line 10 is a flat cable which preferably isused for, for example, connecting two high-frequency circuits inside anelectronic device such as a cell phone. The high-frequency signal line10 includes signal line portions 10-1 to 10-3 and connectors 100 a, 100b as shown in FIG. 1 and FIG. 2.

The signal line portion 10-1 (second signal line) preferably has alinear shape extending in the x-axis direction. As shown in FIG. 3 andFIG. 4, the signal line portion 10-1 includes a dielectric elementassembly 12-1 (second dielectric element assembly), a signal line 20-1(second signal line), a reference ground conductor 22-1 (second groundconductor), an auxiliary ground conductor 24-1 (fourth groundconductor), connecting conductors 25 a, 25 b, and via-hole conductors b1to b6, B1-1, B2-1, B3-1, B4-1.

The dielectric element assembly 12-1 (second dielectric elementassembly) is a linear plate-shaped flexible element linearly extendingin the x-axis direction so as to have two ends when viewed in plan inthe z-axis direction, and including a top surface S1 (third principalsurface) and a bottom surface S2 (fourth principal surface), as shown inFIG. 3 and FIG. 4. The dielectric element assembly 12-1 has a uniform orsubstantially uniform width when viewed in plan in the z-axis direction.The top surface S1 is a principal surface on the positive side in thez-axis direction. The bottom surface S2 is a principal surface on thenegative side in the z-axis direction. The dielectric element assembly12-1 is a laminate including dielectric sheets 18-1 a to 18-1 dlaminated on each other in this order from the positive side to thenegative side in the z-axis direction as shown in FIG. 3 and FIG. 4.

The dielectric sheets 18-1 a to 18-1 d extend in the x-axis directionand have the same or substantially the same shape as the dielectricelement assembly 12 when viewed in plan in the z-axis direction as shownin FIG. 3 and FIG. 4. The dielectric sheets 18-1 a to 18-1 d arepreferably made of a flexible thermoplastic resin such as polyimide orliquid crystal polymer, for example. In the following, the principalsurface of each of the dielectric sheets 18-1 a to 18-1 d that islocated on the positive side in the z-axis direction is referred to astop surface, and the principal surface of each of the dielectric sheets18-1 a to 18-1 d that is located on the negative side in the z-axisdirection is referred to as bottom surface.

The thickness T1 of the dielectric sheet 18-1 b is greater than thethickness T2 of the dielectric sheet 18-1 c as shown in FIG. 4. Thethickness T1 preferably is about 50 μm to about 300 μm, for example,after the lamination of the dielectric sheets 18-1 a to 18-1 d. In thepresent preferred embodiment, the thickness T1 preferably is about 150μm, for example. Moreover, the thickness T2 preferably is about 10 μm toabout 100 μm, for example. In the present preferred embodiment, thethickness T2 preferably is about 50 μm, for example.

The signal line 20-1 is a conductor through which high-frequency signalsare transmitted and which is provided in the dielectric element assembly12-1 as shown in FIG. 3 and FIG. 4. In the present preferred embodiment,the signal line 20-1 preferably is a linear conductor located on the topsurface of the dielectric sheet 18-1 c and extending in the x-axisdirection along the dielectric element assembly 12-1. An end of thesignal line 20-1 on the negative side in the x-axis direction is locatednear an end of the signal line portion 10-1 on the negative side in thex-axis direction. The other end of the signal line 20-1 on the positiveside in the x-axis direction is located near the other end of the signalline portion 10-1 on the positive side in the x-axis direction. Thesignal line 20-1 is preferably made of a metal material including silveror copper and having a low specific resistance. Here, forming the signalline 20-1 on the top surface of the dielectric sheet 18-1 c refers toforming the signal line 20-1 preferably by patterning a metal foil thatis formed preferably by plating on the top surface of the dielectricsheet 18-1 c or forming the signal line 20-1 preferably by patterning ametal foil that is adhered onto the top surface of the dielectric sheet18-1 c. Further, the surface of the signal line 20-1 is smoothed, andtherefore, the surface roughness of a surface of the signal line 20-1which is in contact with the dielectric sheet 18-1 c is greater than thesurface roughness of the other surface of the signal line 20-1 which isnot in contact with the dielectric sheet 18-1 c.

The reference ground conductor 22-1 is a solid conductor layer providedon the positive side in the z-axis direction relative to the signal line20-1 and extends along the signal line 20-1 as shown in FIG. 3 and FIG.4. That is, the reference ground conductor 22-1 is provided on the topsurface S1 side of the dielectric element assembly 12-1 relative to thesignal line 20-1. More specifically, the reference ground conductor 22-1is arranged on the bottom surface of the dielectric sheet 18-1 a so asto extend in the x-axis direction. Thus, the reference ground conductor22-1 is opposed to the signal line 20-1 via the dielectric sheet 18-1 b.The reference ground conductor 22-1 does not have an opening at aposition overlapping with the signal line 20-1. An end of the referenceground conductor 22-1 on the negative side in the x-axis direction islocated near the end of the signal line portion 10-1 on the negativeside in the x-axis direction. Note that, however, as shown in FIG. 3 andFIG. 4, the end of the reference ground conductor 22-1 on the negativeside in the x-axis direction is positioned on the positive side in thex-axis direction relative to the end of the signal line 20-1 on thenegative side in the x-axis direction. The other end of the referenceground conductor 22-1 on the positive side in the x-axis direction islocated near the end of the signal line portion 10-1 on the positiveside in the x-axis direction. Note that, however, as shown in FIG. 3 andFIG. 4, the end of the reference ground conductor 22-1 on the positiveside in the x-axis direction is positioned on the negative side in thex-axis direction relative to the end of the signal line 20-1 on thepositive side in the x-axis direction.

The reference ground conductor 22-1 is made of a metal materialincluding silver or copper and having a low specific resistance. Here,forming the reference ground conductor 22-1 on the bottom surface of thedielectric sheet 18-1 a refers to forming the reference ground conductor22-1 preferably by patterning a metal foil that is formed preferably byplating on the bottom surface of the dielectric sheet 18-1 a or formingthe reference ground conductor 22-1 preferably by patterning a metalfoil that is adhered onto the bottom surface of the dielectric sheet18-1 a. Further, the surface of the reference ground conductor 22-1 issmoothed, and therefore, the surface roughness of a surface of thereference ground conductor 22-1 which is in contact with the dielectricsheet 18-1 a is greater than the surface roughness of the other surfaceof the reference ground conductor 22-1 which is not in contact with thedielectric sheet 18-1 a.

The auxiliary ground conductor 24-1 is a conductor layer provided on thenegative side in the z-axis direction relative to the signal line 20-1and extends along the signal line 20-1 as shown in FIG. 3 and FIG. 4.That is, the auxiliary ground conductor 24-1 is provided on the bottomsurface S2 side of the dielectric element assembly 12-1 relative to thesignal line 20-1. More specifically, the auxiliary ground conductor 24-1is arranged on the top surface of the dielectric sheet 18-1 d so as toextend in the x-axis direction. Thus, the auxiliary ground conductor24-1 is opposed to the signal line 20-1 via the dielectric sheet 18-1 c.An end of the auxiliary ground conductor 24-1 on the negative side inthe x-axis direction is located near the end of the signal line portion10-1 on the negative side in the x-axis direction. The other end of theauxiliary ground conductor 24-1 on the positive side in the x-axisdirection is located near the end of the signal line portion 10-1 on thepositive side in the x-axis direction.

The auxiliary ground conductor 24-1 is made of a metal materialincluding silver or copper and having a low specific resistance. Here,forming the auxiliary ground conductor 24-1 on the top surface of thedielectric sheet 18-1 d refers to forming the auxiliary ground conductor24-1 preferably by patterning a metal foil that is formed preferably byplating on the top surface of the dielectric sheet 18-1 d or forming theauxiliary ground conductor 24-1 preferably by patterning a metal foilthat is adhered onto the top surface of the dielectric sheet 18-1 d.Further, the surface of the auxiliary ground conductor 24-1 is smoothed,and therefore, the surface roughness of a surface of the auxiliaryground conductor 24-1 which is in contact with the dielectric sheet 18-1d is greater than the surface roughness of the other surface of theauxiliary ground conductor 24-1 which is not in contact with thedielectric sheet 18-1 d.

The auxiliary ground conductor 24-1 preferably includes a plurality ofrectangular or substantially rectangular openings 30-1 arranged alongthe x-axis direction as shown in FIG. 3 and FIG. 4. Thus, the auxiliaryground conductor 24-1 preferably has a ladder-shaped configuration. Aportion of the auxiliary ground conductor 24-1 lying between adjacentopenings 30-1 is referred to as “bridge portion 60-1”. The bridgeportion 60-1 extends in the y-axis direction. The plurality of openings30-1 and the plurality of bridge portions 60-1 alternately overlap withthe signal line 20-1 when viewed in plan in the z-axis direction. In thepresent preferred embodiment, the signal line 20-1 extends in the x-axisdirection so as to traverse the centers in the y-axis direction of theopenings 30-1 and the bridge portions 60-1.

As described above, the reference ground conductor 22-1 does not have anopening, while the auxiliary ground conductor 24-1 includes the openings30-1. Thus, the overlapping area of the reference ground conductor 22-1and the signal line 20-1 is greater than the overlapping area of theauxiliary ground conductor 24-1 and the signal line 20-1.

The connecting conductor 25 a is provided on the bottom surface of thedielectric sheet 18-1 a, at a position on the negative side in thex-axis direction relative to the end of the reference ground conductor22-1 on the negative side in the x-axis direction. Thus, the connectingconductor 25 a overlaps with the end of the signal line 20-1 on thenegative side in the x-axis direction when viewed in plan in the z-axisdirection.

The connecting conductor 25 b is provided on the bottom surface of thedielectric sheet 18-1 a, at a position on the positive side in thex-axis direction relative to the end of the reference ground conductor22-1 on the positive side in the x-axis direction. Thus, the connectingconductor 25 b overlaps with the end of the signal line 20-1 on thepositive side in the x-axis direction when viewed in plan in the z-axisdirection.

The plurality of via-hole conductors B1-1 pierce through the dielectricsheet 18-1 b in the z-axis direction at positions on the positive sidein the y-axis direction relative to the signal line 20-1, and arearranged in a row in the x-axis direction with equal intervals, as shownin FIG. 3 and FIG. 4. The plurality of via-hole conductors B2-1 piercethrough the dielectric sheet 18-1 c in the z-axis direction at positionson the positive side in the y-axis direction relative to the signal line20-1, and are arranged in a row in the x-axis direction with equalintervals, as shown in FIG. 2. The via-hole conductors B1-1, B2-1 areconnected to each other to define a single via-hole conductor. Ends ofthe via-hole conductors B1-1 on the positive side in the z-axisdirection are connected to the reference ground conductor 22-1. Ends ofthe via-hole conductors B2-1 on the negative side in the z-axisdirection are connected to the auxiliary ground conductor 24-1, morespecifically to the auxiliary ground conductor 24-1 at positions on thepositive side in the y-axis direction relative to the bridge portion60-1. The via-hole conductors B1-1, B2-1 may be formed preferably byproviding an electrically-conductive paste including silver, tin,copper, or the like, into via holes formed in the dielectric sheets 18-1b, 18-1 c and solidifying the paste.

The plurality of via-hole conductors B3-1 pierce through the dielectricsheet 18-1 b in the z-axis direction at positions on the negative sidein the y-axis direction relative to the signal line 20-1, and arearranged in a row in the x-axis direction with equal intervals, as shownin FIG. 3 and FIG. 4. The plurality of via-hole conductors B4-1 piercethrough the dielectric sheet 18-1 c in the z-axis direction at positionson the negative side in the y-axis direction relative to the signal line20-1, and are arranged in a row in the x-axis direction with equalintervals, as shown in FIG. 2. The via-hole conductors B3-1, B4-1 areconnected to each other to form a single via-hole conductor. Ends of thevia-hole conductors B3-1 on the positive side in the z-axis directionare connected to the reference ground conductor 22-1. Ends of thevia-hole conductors B4-1 on the negative side in the z-axis directionare connected to the auxiliary ground conductor 24-1, more specificallyto the auxiliary ground conductor 24-1 at positions on the negative sidein the y-axis direction relative to the bridge portion 60-1. Thevia-hole conductors B3-1, B4-1 may be formed preferably by providing anelectrically-conductive paste including silver, tin, copper, or thelike, into via holes formed in the dielectric sheets 18-1 b, 18-1 c andsolidifying the paste.

The via-hole conductor b1 (first via-hole conductor) pierces through thedielectric sheet 18-1 a in the z-axis direction as shown in FIG. 3 andFIG. 4. The via-hole conductor b2 pierces through the dielectric sheet18-1 b in the z-axis direction. An end of the via-hole conductor b1 onthe positive side in the z-axis direction is exposed at a portion of thetop surface S1 at the end of the dielectric element assembly 12-1 on thenegative side in the x-axis direction. The other end of the via-holeconductor b1 on the negative side in the z-axis direction is connectedto the connecting conductor 25 a. An end of the via-hole conductor b2 onthe positive side in the z-axis direction is connected to the connectingconductor 25 a. The other end of the via-hole conductor b2 on thenegative side in the z-axis direction is connected to the end of thesignal line 20-1 on the negative side in the x-axis direction. Thus, thevia-hole conductor b1 is electrically coupled to the signal line 20-1via the via-hole conductor b2 and the connecting conductor 25 a.

The via-hole conductor b3 (first via-hole conductor) pierces through thedielectric sheet 18-1 a in the z-axis direction as shown in FIG. 3 andFIG. 4. The via-hole conductor b4 pierces through the dielectric sheet18-1 b in the z-axis direction. An end of the via-hole conductor b3 onthe positive side in the z-axis direction is exposed at a portion of thetop surface S1 at the end of the dielectric element assembly 12-1 on thepositive side in the x-axis direction. The other end of the via-holeconductor b3 on the negative side in the z-axis direction is connectedto the connecting conductor 25 b. An end of the via-hole conductor b4 onthe positive side in the z-axis direction is connected to the connectingconductor 25 b. The other end of the via-hole conductor b4 on thenegative side in the z-axis direction is connected to the end of thesignal line 20-1 on the positive side in the x-axis direction. Thus, thevia-hole conductor b3 is electrically coupled to the signal line 20-1via the via-hole conductor b4 and the connecting conductor 25 b.

The via-hole conductor b5 pierces through the dielectric sheet 18-1 a inthe z-axis direction, and is provided on the positive side in the x-axisdirection relative to the via-hole conductor b1, as shown in FIG. 3 andFIG. 4. An end of the via-hole conductor b5 on the positive side in thez-axis direction is exposed at a portion of the top surface S1 at theend of the dielectric element assembly 12-1 on the negative side in thex-axis direction. The other end of the via-hole conductor b5 on thenegative side in the z-axis direction is connected to the end of thereference ground conductor 22-1 on the negative side in the x-axisdirection.

The via-hole conductor b6 pierces through the dielectric sheet 18-1 a inthe z-axis direction, and is provided on the negative side in the x-axisdirection relative to the via-hole conductor b3, as shown in FIG. 3 andFIG. 4. An end of the via-hole conductor b6 on the positive side in thez-axis direction is exposed at a portion of the top surface S1 at theend of the dielectric element assembly 12-1 on the positive side in thex-axis direction. The other end of the via-hole conductor b6 on thenegative side in the z-axis direction is connected to the end of thereference ground conductor 22-1 on the positive side in the x-axisdirection. The via-hole conductors b1 to b6 may be formed preferably byproviding an electrically-conductive paste including silver, tin,copper, or the like, into via holes formed in the dielectric sheets 18-1a to 18-1 c and solidifying the paste.

The signal line 20-1, the reference ground conductor 22-1, the auxiliaryground conductor 24-1, and the connecting conductors 25 a, 25 bpreferably equal or approximately equal thicknesses. For example, thesignal line 20-1, the reference ground conductor 22-1, the auxiliaryground conductor 24-1, and the connecting conductors 25 a, 25 bpreferably have thicknesses of about 10 μm to about 20 μm.

As described above, the signal line 20-1 is provided between thereference ground conductor 22-1 and the auxiliary ground conductor 24-1which are provided at the opposite sides in the z-axis direction of thesignal line 20-1. That is, the signal line 20-1, the reference groundconductor 22-1, and the auxiliary ground conductor 24-1 define atri-plate stripline structure. The space (the distance in the z-axisdirection) between the signal line 20-1 and the reference groundconductor 22-1 preferably is equal or approximately equal to thethickness T1 of the dielectric sheet 18-1 b as shown in FIG. 4, andpreferably is about 50 μm to about 300 μm, for example. In the presentpreferred embodiment, the space between the signal line 20-1 and thereference ground conductor 22-1 preferably is about 150 μm, for example.The space (the distance in the z-axis direction) between the signal line20-1 and the auxiliary ground conductor 24-1 preferably is equal orapproximately equal to the thickness T2 of the dielectric sheet 18-1 cas shown in FIG. 4, and preferably is about 10 μm to about 100 μm, forexample. In the present preferred embodiment, the space between thesignal line 20-1 and the auxiliary ground conductor 24-1 preferably isabout 50 μm, for example. Thus, the distance in the z-axis directionbetween the signal line 20-1 and the reference ground conductor 22-1 isgreater than the distance in the z-axis direction between the signalline 20-1 and the auxiliary ground conductor 24-1.

The signal line portion 10-2 (first signal line) has a linear shapeextending in the x-axis direction and includes a dielectric elementassembly 12-2 (first dielectric element assembly), external terminals16-1 a to 16-1 d, a signal line 20-2 (first signal line), a referenceground conductor 22-2 (first ground conductor), an auxiliary groundconductor 24-2 (third ground conductor), connecting conductors 43 to 46,and via-hole conductors b7 to b16, B1-2, B2-2, B3-2, B4-2 as shown inFIG. 5 and FIG. 6.

The dielectric element assembly 12-2 (first dielectric element assembly)is a linear plate-shaped flexible element linearly extending in they-axis direction so as to have two ends when viewed in plan in thez-axis direction, and having a top surface S3 (first principal surface)and a bottom surface S4 (second principal surface), as shown in FIG. 5and FIG. 6. The top surface S3 is a principal surface on the positiveside in the z-axis direction. The bottom surface S4 is a principalsurface on the negative side in the z-axis direction. The dielectricelement assembly 12-2 is a laminate including dielectric sheets 18-2 ato 18-2 d laminated on each other in this order from the positive sideto the negative side in the z-axis direction as shown in FIG. 5 and FIG.6.

The dielectric element assembly 12-2 includes a line portion 12-2 a anda connecting portion 12-2 b as shown in FIG. 1 and FIG. 2. The lineportion 12-2 a extends in the y-axis direction as shown in FIG. 1. Theconnecting portion 12-2 b is connected to an end of the line portion12-2 a on the negative side in the y-axis direction and preferably has arectangular or substantially rectangular shape. The width in the x-axisdirection of the connecting portion 12-2 b is greater than the width inthe x-axis direction of the line portion 12-2 a.

The dielectric sheets 18-2 a to 18-2 d extend in the x-axis directionand preferably have the same shape as the dielectric element assembly12-2 when viewed in plan in the z-axis direction as shown in FIG. 5 andFIG. 6. The dielectric sheets 18-2 a to 18-2 d are preferably made of aflexible thermoplastic resin such as polyimide or liquid crystalpolymer, for example. In the following, the principal surface of each ofthe dielectric sheets 18-2 a to 18-2 d that is located on the positiveside in the z-axis direction is referred to as top surface, and theprincipal surface of each of the dielectric sheets 18-2 a to 18-2 d thatis located on the negative side in the z-axis direction is referred toas bottom surface.

The thickness T1 of the dielectric sheet 18-2 b is greater than thethickness T2 of the dielectric sheet 18-2 c as shown in FIG. 6. Thethickness T1 preferably is about 50 μm to about 300 μm, for example,after the lamination of the dielectric sheets 18-2 a to 18-2 d. In thepresent preferred embodiment, the thickness T1 preferably is about 150μm, for example. Moreover, the thickness T2 preferably is about 10 μm toabout 100 μm, for example. In the present preferred embodiment, thethickness T2 preferably is about 50 μm, for example.

The dielectric sheet 18-2 a includes a line portion 40 a and aconnecting portion 42 a as shown in FIG. 5 and FIG. 6. The dielectricsheet 18-2 b includes a line portion 40 b and a connecting portion 42 b.The dielectric sheet 18-2 c includes a line portion 40 c and aconnecting portion 42 c. The dielectric sheet 18-2 d includes a lineportion 40 d and a connecting portion 42 d. The line portions 40 a to 40d define the line portion 12-2 a. The connecting portions 42 a to 42 ddefine the connecting portion 12-2 b.

The signal line 20-2 is a conductor through which high-frequency signalsare transmitted and which is provided in the dielectric element assembly12-2 as shown in FIG. 5 and FIG. 6. In the present preferred embodiment,the signal line 20-2 is a linear conductor provided on the top surfaceof the dielectric sheet 18-2 c and extending in the y-axis directionalong the signal line 20-2. An end of the signal line 20-2 on thenegative side in the y-axis direction is located near an end of thesignal line portion 10-2 on the negative side in the y-axis direction.The other end of the signal line 20-2 on the positive side in the y-axisdirection is located near the other end of the signal line portion 10-2on the positive side in the y-axis direction. The signal line 20-2 ispreferably made of a metal material including silver or copper andhaving a low specific resistance. Here, forming the signal line 20-2 onthe top surface of the dielectric sheet 18-2 c refers to forming thesignal line 20-2 preferably by patterning a metal foil that is formedpreferably by plating on the top surface of the dielectric sheet 18-2 cor forming the signal line 20-2 preferably by patterning a metal foilthat is adhered onto the top surface of the dielectric sheet 18-2 c.Further, the surface of the signal line 20-2 is smoothed, and therefore,the surface roughness of a surface of the signal line 20-2 which is incontact with the dielectric sheet 18-2 c is greater than the surfaceroughness of the other surface of the signal line 20-2 which is not incontact with the dielectric sheet 18-2 c.

The reference ground conductor 22-2 is a solid conductor layer providedon the positive side in the z-axis direction relative to the signal line20-2 and extends along the signal line 20-2 as shown in FIG. 5 and FIG.6. That is, the reference ground conductor 22-2 is provided on the topsurface S3 side of the dielectric element assembly 12-2 relative to thesignal line 20-2. More specifically, the reference ground conductor 22-2is arranged on the bottom surface of the dielectric sheet 18-2 a so asto extend in the y-axis direction. Thus, the reference ground conductor22-2 is opposed to the signal line 20-2 via the dielectric sheet 18-2 b.The reference ground conductor 22-2 does not have an opening at aposition overlapping with the signal line 20-2.

The reference ground conductor 22-2 is preferably made of a metalmaterial including silver or copper and having a low specificresistance. Here, forming the reference ground conductor 22-2 on thebottom surface of the dielectric sheet 18-2 a refers to forming thereference ground conductor 22-2 preferably by patterning a metal foilthat is formed preferably by plating on the bottom surface of thedielectric sheet 18-2 a or forming the reference ground conductor 22-2preferably by patterning a metal foil that is adhered onto the bottomsurface of the dielectric sheet 18-2 a. Further, the surface of thereference ground conductor 22-2 is smoothed, and therefore, the surfaceroughness of a surface of the reference ground conductor 22-2 which isin contact with the dielectric sheet 18-2 a is greater than the surfaceroughness of the other surface of the reference ground conductor 22-2which is not in contact with the dielectric sheet 18-2 a.

The reference ground conductor 22-2 includes a line portion 22-2 a and aterminal portion 22-2 b as shown in FIG. 5 and FIG. 6. The line portion22-2 a is arranged on the bottom surface of the line portion 18-2 a soas to extend in the y-axis direction. The terminal portion 22-2 b isprovided on the bottom surface of the line portion 18-2 a and preferablyhas a rectangular or substantially rectangular rim configuration. Theterminal portion 22-2 b is connected to an end of the line portion 22-2a on the negative side in the y-axis direction.

The auxiliary ground conductor 24-2 is a conductor layer provided on thenegative side in the z-axis direction relative to the signal line 20-2and extends along the signal line 20-2 as shown in FIG. 5 and FIG. 6.That is, the auxiliary ground conductor 24-2 is provided on the bottomsurface S4 side of the dielectric element assembly 12-2 relative to thesignal line 20-2. More specifically, the auxiliary ground conductor 24-2is arranged on the top surface of the dielectric sheet 18-2 d so as toextend in the y-axis direction.

The auxiliary ground conductor 24-2 is preferably made of a metalmaterial including silver or copper and having a low specificresistance. Here, forming the auxiliary ground conductor 24-2 on the topsurface of the dielectric sheet 18-2 d refers to forming the auxiliaryground conductor 24-2 preferably by patterning a metal foil that isformed preferably by plating on the top surface of the dielectric sheet18-2 d or forming the auxiliary ground conductor 24-2 preferably bypatterning a metal foil that is adhered onto the top surface of thedielectric sheet 18-2 d. Further, the surface of the auxiliary groundconductor 24-2 is smoothed, and therefore, the surface roughness of asurface of the auxiliary ground conductor 24-2 which is in contact withthe dielectric sheet 18-2 d is greater than the surface roughness of theother surface of the auxiliary ground conductor 24-2 which is not incontact with the dielectric sheet 18-2 d.

The reference ground conductor 24-2 includes a line portion 24-2 a and aterminal portion 24-2 b as shown in FIG. 5 and FIG. 6. The line portion24-2 a is provided on the top surface of the line portion 18-2 d so asto extend in the y-axis direction. The terminal portion 24-2 b isprovided on the top surface of the line portion 18-2 d and preferablyhas a rectangular or substantially rectangular rim configuration. Theterminal portion 24-2 b is connected to an end of the line portion 24-2a on the negative side in the y-axis direction.

The line portion 24-2 a preferably includes a plurality of rectangularor substantially rectangular openings 30-2 arranged along the y-axisdirection as shown in FIG. 5 and FIG. 6. Thus, the line portion 24-2 apreferably has a ladder-shaped configuration. A portion of the lineportion 24-2 a lying between adjacent openings 30-2 is referred to as“bridge portion 60-2”. The bridge portion 60-2 extends in the x-axisdirection. The plurality of openings 30-2 and the plurality of bridgeportions 60-2 alternately overlap with the signal line 20-2 when viewedin plan in the z-axis direction. In the present preferred embodiment,the signal line 20-2 extends in the y-axis direction so as to traversethe centers in the x-axis direction of the openings 30-2 and the bridgeportions 60-2.

As described above, the reference ground conductor 22-2 does not have anopening, while the auxiliary ground conductor 24-2 includes the openings30-2. Thus, the overlapping area of the reference ground conductor 22-2and the signal line 20-2 is greater than the overlapping area of theauxiliary ground conductor 24-2 and the signal line 20-2.

The connecting conductor 43 is preferably provided on a portion of thetop surface of the dielectric sheet 18-2 c at an end of the dielectricsheet 18-2 c on the positive side in the y-axis direction. Theconnecting conductor 43 is connected to the signal line 20-2 andprotrudes toward the negative side in the x-axis direction relative tothe signal line 20-2. The connecting conductor 43 is preferably made ofa metal material including silver or copper and having a low specificresistance. Here, forming the connecting conductor 43 on the top surfaceof the dielectric sheet 18-2 c refers to forming the connectingconductor preferably by patterning a metal foil that is formedpreferably by plating on the top surface of the dielectric sheet 18-2 cor forming the connecting conductor 43 preferably by patterning a metalfoil that is adhered onto the top surface of the dielectric sheet 18-2c. Further, the surface of the connecting conductor 43 is smoothed, andtherefore, the surface roughness of a surface of the connectingconductor 43 which is in contact with the dielectric sheet 18-2 c isgreater than the surface roughness of the other surface of theconnecting conductor 43 which is not in contact with the dielectricsheet 18-2 c.

The connecting conductor 44 is preferably provided on a portion of thebottom surface of the dielectric sheet 18-2 d at an end of thedielectric sheet 18-2 d on the positive side in the y-axis direction.That is, the connecting conductor 44 is preferably provided on a portionof the bottom surface S4 at an end of the dielectric element assembly12-2 on the positive side in the y-axis direction. The connectingconductor 44 preferably has a rectangular or substantially rectangularshape and overlaps with the connecting conductor 43 when viewed in planin the z-axis direction. The connecting conductor 44 preferably is madeof a metal material including silver or copper and having a low specificresistance. Here, forming the connecting conductor 44 on the bottomsurface of the dielectric sheet 18-2 d refers to forming the connectingconductor 44 preferably by patterning a metal foil that is formedpreferably by plating on the bottom surface of the dielectric sheet 18-2d or forming the connecting conductor 44 preferably by patterning ametal foil that is adhered onto the bottom surface of the dielectricsheet 18-2 d. Further, the surface of the connecting conductor 44 issmoothed, and therefore, the surface roughness of a surface of theconnecting conductor 44 which is in contact with the dielectric sheet18-2 d is greater than the surface roughness of the other surface of theconnecting conductor 44 which is not in contact with the dielectricsheet 18-2 d.

The connecting conductor 45 is provided on a portion of the top surfaceof the dielectric sheet 18-2 d at the end of the dielectric sheet 18-2 don the positive side in the y-axis direction. The connecting conductor45 is connected to an end of the auxiliary ground conductor 24-2 on thepositive side in the y-axis direction. Here, forming the connectingconductor 45 on the top surface of the dielectric sheet 18-2 d refers toforming the connecting conductor 45 preferably by patterning a metalfoil that is formed preferably by plating on the top surface of thedielectric sheet 18-2 d or forming the connecting conductor 45preferably by patterning a metal foil that is adhered onto the topsurface of the dielectric sheet 18-2 d. Further, the surface of theconnecting conductor 45 is smoothed, and therefore, the surfaceroughness of a surface of the connecting conductor 45 which is incontact with the dielectric sheet 18-2 d is greater than the surfaceroughness of the other surface of the connecting conductor 45 which isnot in contact with the dielectric sheet 18-2 d.

The connecting conductor 46 is provided on a portion of the bottomsurface of the dielectric sheet 18-2 d at an end of the dielectric sheet18-2 d on the positive side in the y-axis direction. That is, theconnecting conductor 46 is provided on a portion of the bottom surfaceS4 at the end of the dielectric element assembly 12-2 on the positiveside in the y-axis direction. The connecting conductor 46 is positionedon the positive side in the x-axis direction relative to the connectingconductor 44. The connecting conductor 46 preferably has a rectangularor substantially rectangular shape and overlaps with the connectingconductor 45 when viewed in plan in the z-axis direction. Here, formingthe connecting conductor 46 on the bottom surface of the dielectricsheet 18-2 d refers to forming the connecting conductor 46 preferably bypatterning a metal foil that is formed preferably by plating on thebottom surface of the dielectric sheet 18-2 d or forming the connectingconductor 46 preferably by patterning a metal foil that is adhered ontothe bottom surface of the dielectric sheet 18-2 d. Further, the surfaceof the connecting conductor 46 is smoothed, and therefore, the surfaceroughness of a surface of the connecting conductor 46 which is incontact with the dielectric sheet 18-2 d is greater than the surfaceroughness of the other surface of the connecting conductor 46 which isnot in contact with the dielectric sheet 18-2 d.

The external terminal 16-1 a preferably is a rectangular orsubstantially rectangular conductor which is provided at the center ofthe top surface S3 of the connecting portion 42 a as shown in FIG. 5.When viewed in plan in the z-axis direction, the external terminal 16-1a overlaps with the end of the signal line 20-2 on the negative side inthe y-axis direction. The external terminal 16-1 b preferably is arectangular or substantially conductor which is provided on the topsurface of the connecting portion 42 a, at a position on the negativeside in the x-axis direction relative to the external terminal 16-1 a asshown in FIG. 5. When viewed in plan in the z-axis direction, theexternal terminal 16-1 b overlaps with the terminal portion 22-2 b. Theexternal terminal 16-1 c preferably is a rectangular or substantiallyrectangular conductor which is provided on the top surface of theconnecting portion 42 a, at a position on the negative side in they-axis direction relative to the external terminal 16-1 a as shown inFIG. 5. When viewed in plan in the z-axis direction, the externalterminal 16-1 c overlaps with the terminal portion 22-2 b. The externalterminal 16-1 d preferably is a rectangular or substantially rectangularconductor which is provided on the top surface of the connecting portion42 a, at a position on the positive side in the x-axis directionrelative to the external terminal 16-1 a as shown in FIG. 5. When viewedin plan in the z-axis direction, the external terminal 16-1 d overlapswith the terminal portion 22-2 b.

The external terminals 16-1 a to 16-1 d are preferably made of a metalmaterial including silver or copper and having a low specificresistance. Further, the top surface of the external terminals 16-1 a to16-1 d is plated with Ni/Au. Here, forming the external terminals 16-1 ato 16-1 d on the top surface of the dielectric sheet 18-2 a refers toforming the external terminals 16-1 a to 16-1 d preferably by patterninga metal foil that is formed preferably by plating on the top surface ofthe dielectric sheet 18-2 a or forming the external terminals 16-1 a to16-1 d preferably by patterning a metal foil that is adhered onto thetop surface of the dielectric sheet 18-2 a. Further, the surface of theexternal terminals 16-1 a to 16-1 d is smoothed, and therefore, thesurface roughness of a surface of the external terminals 16-1 a to 16-1d which is in contact with the dielectric sheet 18-2 a is greater thanthe surface roughness of the other surface of the external terminals16-1 a to 16-1 d which is not in contact with the dielectric sheet 18-2a.

The plurality of via-hole conductors B1-2 pierce through the dielectricsheet 18-2 b in the z-axis direction at positions on the negative sidein the x-axis direction relative to the signal line 20-2, and arearranged in a row in the y-axis direction with equal or substantiallyequal intervals, as shown in FIG. 5 and FIG. 6. The plurality ofvia-hole conductors B2-2 pierce through the dielectric sheet 18-2 c inthe z-axis direction at positions on the negative side in the x-axisdirection relative to the signal line 20-2, and are arranged in a row inthe y-axis direction with equal or substantially equal intervals, asshown in FIG. 5. The via-hole conductors B1-2, B2-2 are connected toeach other to define a single via-hole conductor. Ends of the via-holeconductors B1-2 on the positive side in the z-axis direction areconnected to the reference ground conductor 22-2. Ends of the via-holeconductors B2-2 on the negative side in the z-axis direction areconnected to the auxiliary ground conductor 24-2, more specifically tothe auxiliary ground conductor 24-2 at positions on the negative side inthe x-axis direction relative to the bridge portion 60-2. The via-holeconductors B1-2, B2-2 may be formed preferably by providing anelectrically-conductive paste including silver, tin, copper, or thelike, into via holes formed in the dielectric sheets 18-2 b, 18-2 c andsolidifying the paste.

The plurality of via-hole conductors B3-2 pierce through the dielectricsheet 18-2 b in the z-axis direction at positions on the positive sidein the x-axis direction relative to the signal line 20-2, and arearranged in a row in the x-axis direction with equal or substantiallyequal intervals, as shown in FIG. 5 and FIG. 6. The plurality ofvia-hole conductors B4-2 pierce through the dielectric sheet 18-2 c inthe z-axis direction at positions on the positive side in the x-axisdirection relative to the signal line 20-2, and are arranged in a row inthe y-axis direction with equal or substantially equal intervals, asshown in FIG. 5. The via-hole conductors B3-2, B4-2 are connected toeach other to define a single via-hole conductor. Ends of the via-holeconductors B3-2 on the positive side in the z-axis direction areconnected to the reference ground conductor 22-2. Ends of the via-holeconductors B4-2 on the negative side in the z-axis direction areconnected to the auxiliary ground conductor 24-2, more specifically tothe auxiliary ground conductor 24-2 at positions on the positive side inthe x-axis direction relative to the bridge portion 60-2. The via-holeconductors B3-2, B4-2 may be formed preferably by providing anelectrically-conductive paste including silver, tin, copper, or thelike, into via holes formed in the dielectric sheets 18-2 b, 18-2 c andsolidifying the paste.

The via-hole conductor b7 pierces through the connecting portion 42 a ofthe dielectric sheet 18-2 a in the z-axis direction as shown in FIG. 5and FIG. 6. The via-hole conductor b8 pierces through the connectingportion 42 b of the dielectric sheet 18-2 b in the z-axis direction asshown in FIG. 5 and FIG. 6. The via-hole conductors b7, b8 are connectedto each other to define a single via-hole conductor. An end of thevia-hole conductor b7 on the positive side in the z-axis direction isconnected to the external terminal 16-1 a. An end of the via-holeconductor b8 on the negative side in the z-axis direction is connectedto the end of the signal line 20-2 on the negative side in the y-axisdirection. Thus, the external terminal 16-1 a is electrically coupled tothe signal line 20-1 via the via-hole conductors b7, b8.

The via-hole conductor b9 pierces through the dielectric sheet 18-2 c inthe z-axis direction, at a position near the end of the dielectric sheet18-2 c on the positive side in the y-axis direction, as shown in FIG. 5and FIG. 6. The via-hole conductor b10 pierces through the dielectricsheet 18-2 d in the z-axis direction, at a position near the end of thedielectric sheet 18-2 d on the positive side in the y-axis direction, asshown in FIG. 5 and FIG. 6. The via-hole conductors b9, b10 areconnected to each other to define a single via-hole conductor. An end ofthe via-hole conductor b9 on the positive side in the z-axis directionis connected to the connecting conductor 43. An end of the via-holeconductor b10 on the negative side in the z-axis direction is connectedto the connecting conductor 44. Thus, the connecting conductor 44 iselectrically coupled to the signal line 20-2 via the via-hole conductorsb9, b10 and the connecting conductor 43. The signal line 20-2 isconnected between the external terminal 16-1 a and the connectingconductor 44. The via-hole conductors b9, b10 may be formed preferablyby providing an electrically-conductive paste including silver, tin,copper, or the like, into via holes formed in the dielectric sheets 18-2c, 18-2 d and solidifying the paste.

The via-hole conductor b11 pierces through the dielectric sheet 18-2 bin the z-axis direction, at a position near an end of the dielectricsheet 18-2 b on the positive side in the y-axis direction, as shown inFIG. 5 and FIG. 6. The via-hole conductor b12 pierces through thedielectric sheet 18-2 c in the z-axis direction, at a position near theend of the dielectric sheet 18-2 c on the positive side in the y-axisdirection, as shown in FIG. 5 and FIG. 6. The via-hole conductor b13pierces through the dielectric sheet 18-2 d in the z-axis direction, ata position near the end of the dielectric sheet 18-2 d on the positiveside in the y-axis direction, as shown in FIG. 5 and FIG. 6. Thevia-hole conductors b11 to b13 are connected to one another to define asingle via-hole conductor. An end of the via-hole conductor b11 on thepositive side in the z-axis direction is connected to an end of thereference ground conductor 22-1 on the positive side in the y-axisdirection. An end of the via-hole conductor b12 on the negative side inthe z-axis direction is connected to the connecting conductor 45. An endof the via-hole conductor b13 on the positive side in the z-axisdirection is connected to the connecting conductor 45. The other end ofthe via-hole conductor b13 on the negative side in the z-axis directionis connected to the connecting conductor 46. Thus, the connectingconductor 46 is electrically coupled to the reference ground conductor22-2 and the auxiliary ground conductor 24-2 via the via-hole conductorsb11 to b13 and the connecting conductor 45. The via-hole conductors b11,b13 may be formed preferably by providing an electrically-conductivepaste including silver, tin, copper, or the like, into via holes formedin the dielectric sheets 18-2 b to 18-2 d and solidifying the paste.

The via-hole conductor b14 pierces through the connecting portion 42 aof the dielectric sheet 18-2 a in the z-axis direction as shown in FIG.5 and FIG. 6. An end of the via-hole conductor b14 on the positive sidein the z-axis direction is connected to the external terminal 16-1 b.The other end of the via-hole conductor b14 on the negative side in thez-axis direction is connected to the connecting portion 22-2 b. Thus,the external terminal 16-1 b is electrically coupled to the referenceground conductor 22-2 via the via-hole conductor b14.

The via-hole conductor b15 pierces through the connecting portion 42 aof the dielectric sheet 18-2 a in the z-axis direction as shown in FIG.5 and FIG. 6. An end of the via-hole conductor b15 on the positive sidein the z-axis direction is connected to the external terminal 16-1 c.The other end of the via-hole conductor b15 on the negative side in thez-axis direction is connected to the connecting portion 22-2 b. Thus,the external terminal 16-1 c is electrically coupled to the referenceground conductor 22-2 via the via-hole conductor b15.

The via-hole conductor b16 pierces through the connecting portion 42 aof the dielectric sheet 18-2 a in the z-axis direction as shown in FIG.5 and FIG. 6. An end of the via-hole conductor b16 on the positive sidein the z-axis direction is connected to the external terminal 16-1 d.The other end of the via-hole conductor b16 on the negative side in thez-axis direction is connected to the connecting portion 22-2 b. Thus,the external terminal 16-1 c is electrically coupled to the referenceground conductor 22-2 via the via-hole conductor b16. The via-holeconductors b9 to b16 may be formed preferably by providing anelectrically-conductive paste including silver, tin, copper, or thelike, into via holes formed in the dielectric sheets 18-2 a to 18-2 dand solidifying the paste.

The external terminals 16-1 a to 16-1 d, the signal line 20-2, thereference ground conductor 22-2, the auxiliary ground conductor 24-2,and the connecting conductors 43 to 46 preferably have equal orsubstantially equal thicknesses. For example, the external terminals16-1 a to 16-1 d, the signal line 20-2, the reference ground conductor22-2, the auxiliary ground conductor 24-2, and the connecting conductors43 to 46 preferably have thicknesses of about 10 μm to about 20 μm.

As described above, the signal line 20-2 is provided between thereference ground conductor 22-2 and the auxiliary ground conductor 24-2which are provided at the opposite sides in the z-axis direction of thesignal line 20-2. That is, the signal line 20-2, the reference groundconductor 22-2, and the auxiliary ground conductor 24-2 define atri-plate stripline structure. The space (the distance in the z-axisdirection) between the signal line 20-2 and the reference groundconductor 22-2 preferably is equal or approximately equal to thethickness T1 of the dielectric sheet 18-2 b as shown in FIG. 6, andpreferably is about 50 μm to about 300 μm, for example. In the presentpreferred embodiment, the space between the signal line 20-2 and thereference ground conductor 22-2 preferably is about 150 μm, for example.The space (the distance in the z-axis direction) between the signal line20-2 and the auxiliary ground conductor 24-2 preferably is equal orapproximately equal to the thickness T2 of the dielectric sheet 18-2 cas shown in FIG. 6, and preferably is about 10 μm to about 100 μm, forexample. In the present preferred embodiment, the space between thesignal line 20-2 and the auxiliary ground conductor 24-2 preferably isabout 50 μm, for example. Thus, the distance in the z-axis directionbetween the signal line 20-2 and the reference ground conductor 22-2 isgreater than the distance in the z-axis direction between the signalline 20-2 and the auxiliary ground conductor 24-2.

The signal line portions 10-1, 10-2 which have the above-describedconfiguration are joined together to define a single high-frequencysignal line 10 as shown in FIG. 2. More specifically, as shown in FIG. 2and FIG. 7, a portion of the top surface S1 at the end of the dielectricelement assembly 12-1 on the negative side in the x-axis direction and aportion of the bottom surface S4 at the end of the dielectric elementassembly 12-2 on the positive side in the y-axis direction are joinedtogether. In the present preferred embodiment, a portion of the topsurface S1 at the end of the dielectric element assembly 12-1 on thenegative side in the x-axis direction and a portion of the bottomsurface S4 at the end of the dielectric element assembly 12-2 on thepositive side in the y-axis direction are welded together. Thus, thesignal line portion 10-1 and the signal line portion 10-2 are joinedtogether, and the joint portion of the dielectric element assembly 12-1and the dielectric element assembly 12-2 includes a corner (a bentportion which is bent in a planar direction of the high-frequency signalline 10).

Further, as shown in FIG. 7, the via-hole conductor b1 is connected tothe connecting conductor 44. Thus, the signal line 20-1 and the signalline 20-2 are electrically coupled together. The via-hole conductor b5is connected to the connecting conductor 46. Thus, the reference groundconductors 22-1, 22-2 and the auxiliary ground conductors 24-1, 24-2 areelectrically coupled together.

The signal line portion 10-3 preferably has the same or substantiallythe same configuration as the signal line portion 10-2. Morespecifically, the signal line portion 10-3 has a configuration of linesymmetry with respect to the signal line portion 10-2 about a lineextending in the y-axis direction so as to traverse the center in thex-axis direction of the signal line portion 10-2. Therefore, theconnecting conductor 43 protrudes from the signal line 20-2 toward thenegative side in the x-axis direction. The connecting conductor 44 isarranged so as to overlap with the connecting conductor 43 when viewedin plan in the z-axis direction. Therefore, the connecting conductors45, are provided on the negative side in the x-axis direction relativeto the connecting conductor 44 when viewed in plan in the z-axisdirection.

Next, joining of the signal line portion 10-1 and the signal lineportion 10-3 is described. As shown in FIG. 2, a portion of the topsurface S1 at the end of the dielectric element assembly 12-1 on thepositive side in the x-axis direction and a portion of the bottomsurface S6 at the end of the dielectric element assembly 12-3 on thepositive side in the y-axis direction are joined together. In thepresent preferred embodiment, a portion of the top surface S1 at the endof the dielectric element assembly 12-1 on the positive side in thex-axis direction and a portion of the bottom surface S6 at the end ofthe dielectric element assembly 12-3 on the positive side in the y-axisdirection are welded together. Thus, the signal line portion 10-1 andthe signal line portion 10-3 are joined together, and the joint portionof the dielectric element assembly 12-1 and the dielectric elementassembly 12-3 includes a corner (a bent portion which is bent in aplanar direction of the high-frequency signal line 10).

Further, the via-hole conductor b3 is connected to the connectingconductor 44. Thus, the signal line 20-1 and the signal line 20-2 areelectrically coupled together. The via-hole conductor b6 is connected tothe connecting conductor 46. Thus, the reference ground conductors 22-1,22-2 and the auxiliary ground conductors 24-1, 24-2 are electricallycoupled together.

As described above, the signal line portions 10-1 to 10-3 are joinedtogether such that the high-frequency signal line 10 has a “

”-shape as shown in FIG. 1.

In the high-frequency signal line 10 that has the above-describedconfiguration, the characteristic impedances of the signal lines 20-1,20-2 periodically vary between impedance Z1 and impedance Z2. Morespecifically, in the section A1 where the signal lines 20-1, 20-2overlap with the openings 30-1, 30-2, relatively small capacitance isgenerated between the signal lines 20-1, 20-2 and the auxiliary groundconductors 24-1, 24-2. Therefore, the characteristic impedances of thesignal lines 20-1, 20-2 in the section A1 are relatively high impedanceZ1.

On the other hand, in the section A2 where the signal lines 20-1, 20-2overlap with the bridge portions 60-1, 60-2, relatively largecapacitance is generated between the signal lines 20-1, 20-2 and theauxiliary ground conductors 24-1, 24-2. Therefore, the characteristicimpedances of the signal lines 20-1, 20-2 in the section A2 arerelatively low impedance Z2. The section A1 and the section A2 arealternately arranged in the x-axis direction. Thus, the characteristicimpedances of the signal lines 20-1, 20-2 periodically vary betweenimpedance Z1 and impedance Z2. The impedance Z1 preferably is about 55Ω,for example, and the impedance Z2 preferably is about 45Ω, for example.The average characteristic impedance across the entire signal lines20-1, 20-2 preferably is about 50Ω, for example.

The connectors 100 a, 100 b are mounted on the top surfaces of theconnecting portions 12-2 b, 12-3 b, respectively, as shown in FIG. 1.Since the connectors 100 a, 100 b have the same configuration, theconfiguration of the connector 100 a is described below as an example.FIG. 8 is an external perspective view of the connector 100 a of thehigh-frequency signal line 10. FIG. 9 is a cross-sectional structureview of the connector 100 a of the high-frequency signal line 10.

The connector 100 a includes a connector body 102, external terminals104, 106, a center conductor 108, and an external conductor 110 as shownin FIG. 1, FIG. 8, and FIG. 9. The connector body 102 includes arectangular or substantially rectangular plate member and a cylindricalmember coupled thereon, and is made of an insulating material such asresins.

The external terminal 104 is provided at a position on a surface of theplate member of the connector body 102 on the negative side in thez-axis direction so as to face the external terminal 16-1 a. Theexternal terminal 106 is provided at a position on the surface of theplate member of the connector body 102 on the negative side in thez-axis direction so as to correspond to the external terminals 16-1 b to16-1 d.

The center conductor 108 is provided at the center of the cylindricalmember of the connector body 102 and is connected to the externalterminal 104. The center conductor 108 is a signal terminal throughwhich high-frequency signals are to be input/output. The externalconductor 110 is provided on the inner circumferential surface of thecylindrical member of the connector body 102, and is connected to theexternal terminal 106. The external conductor 110 is a ground terminalto be kept at a ground potential.

The connector 100 a thus configured is mounted on the top surface of theconnecting portion 12-2 b such that the external terminal 104 isconnected to the external terminal 16-1 a and the external terminal 106is connected to the external terminals 16-1 b to 16-1 d as shown in FIG.8 and FIG. 9. As a result, the signal lines 20-1, 20-2 are electricallycoupled to the center conductor 108. The reference ground conductors22-1, 22-2 and the auxiliary ground conductors 24-1, 24-2 areelectrically coupled to the external conductor 110.

The high-frequency signal line 10 is used as described below. FIG. 10 isa perspective view of an electronic device 200 including thehigh-frequency signal line 10. In FIG. 10, the top-to-bottom directionis defined as Z-axis direction. The longitudinal direction of theelectronic device 200 when viewed in plan in the Z-axis direction isdefined as X-axis direction. The transverse direction of the electronicdevice 200 when viewed in plan in the Z-axis direction is defined asY-axis direction.

The electronic device 200 includes the high-frequency signal line 10,circuit boards 202 a, 202 b, a battery pack (metallic body) 206, and ahousing 210.

The circuit board 202 a includes, for example, a transmission orreception circuit including an antenna. The circuit board 202 bincludes, for example, a power circuit. The battery pack 206 is, forexample, a lithium-ion rechargeable battery, and the surface of thebattery pack 206 is covered with a metal cover. The circuit board 202 a,the battery pack 206, and the circuit board 202 b are arranged in thisorder, from the negative side to the positive side in the X-axisdirection.

Unshown receptacles are provided on the principal surfaces of thecircuit boards 202 a, 202 b which are on the positive side in the Z-axisdirection. The receptacles are connected to the connectors 100 a, 100 b(although not shown in FIG. 10). With this arrangement, high-frequencysignals to be transmitted between the circuit boards 202 a, 202 b at afrequency of, for example, 2 GHz are applied to the center conductors108 of the connectors 100 a, 100 b via the receptacles. Moreover, theexternal conductors 110 of the connectors 100 a, 100 b are kept at aground potential via the circuit boards 202 a, 202 b and thereceptacles. With this arrangement, the high-frequency signal line 10defines a connection between the circuit boards 202 a, 202 b.

Here, the top surface S1 of the dielectric element assembly 12-1 is incontact with a lateral surface of the battery pack 206 on the negativeside in the Y-axis direction. The dielectric element assembly 12 and thebattery pack 206 are secured together by an adhesive agent, or the like.Therefore, the reference ground conductors 22-1, 22-2 in a solid form,which do not have an opening, are present between the signal lines 20-1,20-2 and the battery pack 206.

Hereinafter, a non-limiting example of a manufacturing method of thehigh-frequency signal line 10 is described with reference to thedrawings. FIG. 11 is a plan view of a mother dielectric element assembly112. FIG. 12 through FIG. 16 are cross-sectional views of thehigh-frequency signal line 10 in the steps of compression bonding.

First, through the steps which will be described below, the signal lineportions 10-1 to 10-3 are formed in a matrix arrangement over the motherdielectric element assembly 112 that is formed by laminating motherdielectric sheets 118 a to 118 d as shown in FIG. 11.

First, a mother dielectric sheet 118 c is prepared which is made of athermoplastic resin, with one of its principal surfaces being entirelycovered with a copper foil (metal film). Specifically, a copper foil isadhered onto one of the principal surfaces of the mother dielectricsheet 118 c. Further, the copper-foiled surface of the mother dielectricsheet 118 c is, for example, galvanized for anti-corrosion purposes andis thus smoothened. The mother dielectric sheet 118 c is made of aliquid crystal polymer. The thickness of the copper foil preferably isabout 10 μm to about 20 μm.

Then, mother dielectric sheets 118 a, 118 d are prepared which are madeof a thermoplastic resin, with both principal surfaces being entirelycovered with a copper foil (metal film). Specifically, a copper foil isadhered onto both principal surfaces of the mother dielectric sheets 118a, 118 d. Further, the copper-foiled surfaces of the mother dielectricsheets 118 a, 118 d are, for example, galvanized for anti-corrosionpurposes and are thus smoothened. The mother dielectric sheets 118 a,118 d are made of a liquid crystal polymer. The thickness of the copperfoil preferably is about 10 μm to about 20 μm.

Then, the copper foil formed on the top surface of the mother dielectricsheet 118 a is patterned, such that the external terminals 16-1 a to16-1 d shown in FIG. 5 and the external terminals 16-1 a to 16-1 d ofthe signal line portion 10-3 are formed on the top surface of the motherdielectric sheet 118 a. Further, the copper foil formed on the bottomsurface of the mother dielectric sheet 118 a is patterned, such that thereference ground conductors 22-1, 22-2 and the connecting conductors 25a, 25 b shown in FIG. 3 and FIG. 5 and the reference ground conductor22-2 and the connecting conductors 25 a, 25 b of the signal line portion10-3 are formed on the bottom surface of the mother dielectric sheet 118a. In this step, as shown in FIG. 11, on the top surface of the motherdielectric sheet 118 a, the external terminals 16-1 a to 16-1 d areformed at the positions where the dielectric sheet 18-2 a is to beformed. Likewise, on the top surface of the mother dielectric sheet 118a, the external terminals 16-1 a to 16-1 d of the signal line portion10-3 are formed at the positions where the dielectric sheet 18-3 a is tobe formed. Likewise, on the bottom surface of the mother dielectricsheet 118 a, the reference ground conductor 22-1 and the connectingconductors 25 a, 25 b are formed at the positions where the dielectricsheet 18-1 a is to be formed. Likewise, on the bottom surface of themother dielectric sheet 118 a, the reference ground conductor 22-2 isformed at the position where the dielectric sheet 18-2 a is to beformed. Specifically, a resist which has the same shape as the externalterminals 16-1 a to 16-1 d shown in FIG. 5 and the external terminals16-1 a to 16-1 d of the signal line portion 10-3 is printed on thecopper foil on the top surface of the mother dielectric sheet 118 a.Further, a resist which has the same shape as the reference groundconductors 22-1, 22-2 shown in FIG. 5 and the connecting conductors 25a, 25 b is printed on the copper foil on the bottom surface of themother dielectric sheet 118 a. Then, etching is performed on the copperfoil such that portions of the copper foil which are not covered withthe resist are removed. Thereafter, a resist solution is sprayed toremove the resist. In this way, the external terminals 16-1 a to 16-1 dshown in FIG. 5 and the external terminals 16-1 a to 16-1 d of thesignal line portion 10-3 are photolithographically formed on the topsurface of the mother dielectric sheet 118 a, and the reference groundconductors 22-1, 22-2 shown in FIG. 3 and FIG. 5, and the referenceground conductor 22-2 of the signal line portion 10-3, and theconnecting conductors 25 a, 25 b are photolithographically formed on thebottom surface of the mother dielectric sheet 118 a.

Then, the signal lines 20-1, 20-2 shown in FIG. 3 and FIG. 5, the signalline 20-2 of the signal line portion 10-3, the connecting conductor 43,and the connecting conductor 20-2 of the signal line portion 10-3 (notshown) are formed on the top surface of the mother dielectric sheet 118c. Further, the auxiliary ground conductors 24-1, 24-2 shown in FIG. 3and FIG. 5, the auxiliary ground conductor 24-2 of the signal lineportion 10-3, the connecting conductor 45, and the connecting conductor45 of the signal line portion 10-3 are formed on the top surface of themother dielectric sheet 118 d, while the connecting conductors 44, 46and the connecting conductors 44, 46 of the signal line portion 10-3(not shown) are formed on the bottom surface of the mother dielectricsheet 118 d. Note that the formation process of the signal line 20-1 andthe like is the same as that of the external terminals 16-1 a to 16-1 d,and therefore, the description thereof is herein omitted.

Then, portions of the mother dielectric sheets 118 a to 118 d at whichthe via-hole conductors b2, b4, b7 to b16, B1-1, B2-1, B3-1, B4-1, B1-2,B2-2, B3-2, B4-2 are to be formed are irradiated with a laser beam suchthat through holes are formed. Then, an electrically-conductive paste isprovided into the through holes to form the via-hole conductors b2, b4,b7 to b16, B1-1, B2-1, B3-1, B4-1, B1-2, B2-2, B3-2, B4-2. Note that, inthis step, the via-hole conductors b1, b3, b5, b6 are not formed.

Then, as shown in FIG. 12 and FIG. 13, the mother dielectric sheets 118a to 118 d are laminated in this order from the positive side to thenegative side in the z-axis direction, and the resultant structure issubjected to the compression bonding and heating processes. In thisstep, uncured via-hole conductors b2, b4, b7 to b16, B1-1, B2-1, B3-1,B4-1, B1-2, B2-2, B3-2, B4-2 are solidified so that the via-holeconductors b2, b4, b7 to b16, B1-1, B2-1, B3-1, B4-1, B1-2, B2-2, B3-2,B4-2 are formed. Further, the mother dielectric sheets 118 a to 118 dare softened and melted so that the mother dielectric sheets 118 a to118 d are united together, such that the mother dielectric elementassembly 112 is formed.

After formation of the mother dielectric element assembly 112, as shownin FIG. 14, portions of the mother dielectric element assembly 112 atwhich the via-hole conductors b1, b3, b5, b6 are to be formed areirradiated with a laser beam such that through holes are formed. Then,as shown in FIG. 15, an electrically-conductive paste is provided intothe through holes to form uncured via-hole conductors b1, b3, b5, b6.Through the above steps, the process of forming the signal line portions10-1 to 10-3 in a matrix arrangement over the mother dielectric elementassembly 112 formed by laminating the mother dielectric sheets 118 a to118 d is completed.

Then, the mother dielectric element assembly 112 is stamped (cut) out,such that a plurality of signal line portions 10-1 to 10-3 are obtained.Through the above steps, the process of forming the signal line portions10-1 to 10-3 is completed.

Then, as shown in FIG. 16, the signal line portion 10-1 and the signalline portion 10-2 are joined together such that the joint portion of thesignal line portion 10-1 and the signal line portion 10-2 includes acorner (a bent portion which is bent in a planar direction of thehigh-frequency signal line 10). Specifically, a portion of the topsurface S1 at the end of the dielectric element assembly 12-1 on thenegative side in the x-axis direction and a portion of the bottomsurface S4 at the end of the dielectric element assembly 12-2 on thepositive side in the y-axis direction are arranged so as to face eachother, and these portions are subjected to the heating process and thecompression process such that they are joined together. In this step,the via-hole conductor b1 and the connecting conductor 44 are connectedtogether, and the via-hole conductor b5 and the connecting conductor 46are connected together. Then, the heating process is performed tosolidify uncured via-hole conductors b1, b5, such that the via-holeconductors b1, b5 are formed. And, an alloy is formed at the connectingportion of the via-hole conductor b1 and the connecting conductor 44,and an alloy is formed at the connecting portion of the via-holeconductor b5 and the connecting conductor 46. As a result, the signalline 20-1 and the signal line 20-2 are electrically coupled together,and the reference ground conductors 22-1, 22-2 and the auxiliary groundconductors 24-1, 24-2 are electrically coupled together. Further, aportion of the top surface S1 at the end of the dielectric elementassembly 12-1 on the negative side in the x-axis direction and a portionof the bottom surface S4 at the end of the dielectric element assembly12-2 on the positive side in the y-axis direction are softened andmelted so that these portions are welded together. Note that the step ofjoining together the signal line portion 10-1 and the signal lineportion 10-3 is the same as the step of joining together the signal lineportion 10-1 and the signal line portion 10-2, and therefore, thedescription thereof is herein omitted.

Lastly, the connectors 100 a, 100 b are mounted onto the connectingportions 12-2 b, 12-3 b using a solder. As a result, the high-frequencysignal line 10 shown in FIG. 1 is obtained.

According to the non-limiting example of a manufacturing method of thehigh-frequency signal line 10 that has the above-describedconfiguration, the manufacturing cost of the high-frequency signal line10 that has a bent configuration is significantly reduced. FIG. 17 is aplan view of a mother laminate 712 in manufacture of a dielectricelement assembly 612 of a high-frequency signal line according to acomparative example.

The high-frequency signal line of the comparative example has a “

”-shape as shown in FIG. 17 and is not divided into the plurality ofsignal line portions 10-1 to 10-3 as in the high-frequency signal line10. In manufacture of the high-frequency signal line of the comparativeexample which has such a configuration, there are large spaces betweenadjacent dielectric element assemblies 612 in the mother laminate 712because the dielectric element assemblies 612 have corners. Accordingly,the number of high-frequency signal lines obtained from a single motherlaminate 712 decreases, and the manufacturing cost of the high-frequencysignal lines increases.

In view of such circumstances, the high-frequency signal line 10 isconfigured so as to be divisible into the signal line portions 10-1 to10-3. The signal line portion 10-1 and the signal line portion 10-2 arejoined together such that the joint portion of the signal line portion10-1 and the signal line portion 10-2 includes a corner. Likewise, thesignal line portion 10-1 and the signal line portion 10-3 are joinedtogether such that the joint portion of the signal line portion 10-1 andthe signal line portion 10-3 includes a corner. Thus, the cornerspreferably are formed in the high-frequency signal line after thestamping process is performed on the mother dielectric element assembly112 to obtain the signal line portions 10-1 to 10-3. Therefore, as shownin FIG. 11, the signal line portions 10-1 to 10-3 are capable of beingformed in a matrix arrangement over the mother dielectric elementassembly 112 with the spaces between adjacent signal line portions 10-1to 10-3 being reduced. In the present preferred embodiment, the signalline portions 10-1 to 10-3 preferably have a linear shape, andtherefore, the spaces between adjacent signal line portions 10-1 to 10-3are further reduced. Thus, in the high-frequency signal line 10 and themanufacturing method thereof, a larger number of high-frequency signallines 10 is obtained from a single mother dielectric element assembly112. As a result, according to the high-frequency signal line 10 and themanufacturing method thereof, the manufacturing cost of thehigh-frequency signal line 10 that has a bent configuration issignificantly reduced.

In the high-frequency signal line 10 and the manufacturing methodthereof, the via-hole conductor b1 and the connecting conductor 44 areconnected together, and the via-hole conductor b5 and the connectingconductor 46 are connected together. In connecting these elements,uncured via-hole conductors b1, b5 which are kept in contact with theconnecting conductors 44, 46, respectively, are subjected to the heatingprocess and the compression process. In this way, the via-holeconductors b1, b5 are solidified so that alloy layers are formed at theconnecting portions of the via-hole conductors b1, b5 and the connectingconductors 44, 46. Therefore, the via-hole conductors b1, b5 and theconnecting conductors 44, 46 are more strongly connected.

In the high-frequency signal line 10 and the manufacturing methodthereof, the signal line portion 10-1 and the signal line portions 10-2,10-3 are welded together. Therefore, according to the high-frequencysignal line 10 and the manufacturing method thereof, the signal lineportion 10-1 and the signal line portions 10-2, 10-3 are more stronglyjoined.

In the high-frequency signal line 10 and the manufacturing methodthereof, connection of the via-hole conductors b1, b5 and the connectingconductors 44, 46 and welding of the signal line portion 10-1 and thesignal line portion 10-2 preferably are carried out in the same step.Therefore, in the high-frequency signal line 10 and the manufacturingmethod thereof, the manufacturing process is simplified.

According to the high-frequency signal line 10, a significant reductionin thickness is realized. More specifically, in the high-frequencysignal line 10, in the section A1, the signal lines 20-1, 20-2 do notoverlap with the auxiliary ground conductors 24-1, 24-2 when viewed inplan in the z-axis direction. Therefore, capacitance is unlikely to begenerated between the signal lines 20-1, 20-2 and the auxiliary groundconductors 24-1, 24-2. Thus, even when the distance in the z-axisdirection between the signal lines 20-1, 20-2 and the auxiliary groundconductors 24-1, 24-2 is reduced, the capacitance generated between thesignal lines 20-1, 20-2 and the auxiliary ground conductors 24-1, 24-2is not excessively large. Thus, the characteristic impedance of thesignal lines 20-1, 20-2 is unlikely to deviate from a predeterminedcharacteristic impedance (e.g., about 50Ω). As a result, the thicknessis significantly reduced while the characteristic impedance of thehigh-frequency signal line 10 is maintained at a predeterminedcharacteristic impedance.

According to the high-frequency signal line 10, when the high-frequencysignal line 10 is adhered to a metallic body such as the battery pack206, variation in the characteristic impedance of the signal lines 20-1,20-2 is prevented. More specifically, the high-frequency signal line 10is adhered to the battery pack 206 such that the reference groundconductors 22-1, 22-2 in a solid form are provided between the signallines 20-1, 20-2 and the battery pack 206. With this arrangement, thesignal lines 20-1, 20-2 and the battery pack 206 would not face eachother via an opening, so that generation of capacitance between thesignal lines 20-1, 20-2 and the battery pack 206 is prevented. As aresult, even when the high-frequency signal line 10 is adhered to thebattery pack 206, a decrease of the characteristic impedance of thesignal lines 20-1, 20-2 is prevented.

Hereinafter, a non-limiting example of a manufacturing method of thehigh-frequency signal line 10 according to a modification of a preferredembodiment of the present invention is described with reference to thedrawings. FIG. 18 through FIG. 20 are cross-sectional views of ahigh-frequency signal line 10 a in the steps of compression bonding.

In the non-limiting example of a manufacturing method of thehigh-frequency signal line 10 according to the above-described preferredembodiment, as shown in FIG. 14, after the step of laminating the motherdielectric sheets 118 a to 118 d to form the dielectric element assembly12-1, through holes are formed in the dielectric element assembly 12-1,and moreover, an electrically-conductive paste is provided into thethrough holes to form uncured via-hole conductors b1, b3, b5, b6. On theother hand, in the manufacturing method of the high-frequency signalline 10 according to the present modification, as shown in FIG. 18,uncured via-hole conductors b1, b3, b5, b6 are formed before the step oflaminating the mother dielectric sheets 118 a to 118 d to form themother dielectric element assembly 112 (i.e., the dielectric elementassembly 12-1). That is, after through holes are formed in the motherdielectric sheet 118 a, an electrically-conductive paste is providedinto the through holes to form uncured via-hole conductors b1, b3, b5,b6.

Further, as shown in FIG. 19, the heating process and the compressionprocess are performed on the mother dielectric sheet 118 a in whichuncured via-hole conductors b1, b3, b5, b6 have been formed and themother dielectric sheets 118 b to 118 c, such that the mother dielectricelement assembly 112 is formed. In the compression bonding step (thestep of forming the dielectric element assembly 12-1), the heatingprocess is performed at a temperature such that the uncured via-holeconductors b1, b3, b5, b6 (i.e., the electrically-conductive paste)would not solidify. Through the above steps, the step of forming themother dielectric element assembly 112 (the dielectric element assembly12-1) is completed.

Then, the mother dielectric element assembly 112 is stamped (cut) out,such that a plurality of signal line portions 10-1 to 10-3 are obtained.Through the above steps, the process of forming the signal line portions10-1 to 10-3 is completed.

Then, as shown in FIG. 20, the signal line portion 10-1 and the signalline portion 10-2 are joined together such that the joint portion of thesignal line portion 10-1 and the signal line portion 10-2 includes acorner. Specifically, a portion of the top surface S1 at the end of thedielectric element assembly 12-1 on the negative side in the x-axisdirection and a portion of the bottom surface S4 at the end of thedielectric element assembly 12-2 on the positive side in the y-axisdirection are arranged so as to face each other, and these portions aresubjected to the heating process and the compression process such thatthey are joined together. In this step, the via-hole conductor b1 andthe connecting conductor 44 are connected together, and the via-holeconductor b5 and the connecting conductor 46 are connected together.Then, the heating process is performed to solidify uncured via-holeconductors b1, b5, such that the via-hole conductors b1, b5 are formed.Moreover, an alloy is formed at the connecting portion of the via-holeconductor b1 and the connecting conductor 44, and an alloy is formed atthe connecting portion of the via-hole conductor b5 and the connectingconductor 46. As a result, the signal line 20-1 and the signal line 20-2are electrically coupled together, and the reference ground conductors22-1, 22-2 and the auxiliary ground conductors 24-1, 24-2 areelectrically coupled together. Further, a portion of the top surface S1at the end of the dielectric element assembly 12-1 on the negative sidein the x-axis direction and a portion of the bottom surface S4 at theend of the dielectric element assembly 12-2 on the positive side in they-axis direction are softened and melted so that these portions arewelded together. Note that the step of joining together the signal lineportion 10-1 and the signal line portion 10-3 is the same as the step ofjoining together the signal line portion 10-1 and the signal lineportion 10-2, and therefore, the description thereof is herein omitted.

According to the non-limiting example of a manufacturing method of thehigh-frequency signal line 10 according to a modification of a preferredembodiment of the present invention, uncured via-hole conductors b1, b3,b5, b6 are formed before the step of laminating the mother dielectricsheets 118 a to 118 d to form the mother dielectric element assembly 112(i.e., the dielectric element assembly 12-1). Thus, uncured via-holeconductors b1, b3, b5, b6 are formed in the mother dielectric sheet 118a. Therefore, it is not necessary to form through holes in thedielectric element assembly 12-1 after the lamination and provide theelectrically-conductive paste therein. Thus, according to themanufacturing method of the high-frequency signal line 10, themanufacturing process of the high-frequency signal line 10 issimplified.

Hereinafter, a high-frequency signal line according to the firstmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 21 is a plan view of ahigh-frequency signal line 10 a according to the first modification whenviewed in plan in the z-axis direction. Note that the connectors 100 a,100 b are omitted from FIG. 21.

The high-frequency signal line 10 a is different from the high-frequencysignal line 10 in the shape of the high-frequency signal line 10 a andthe shape of the signal line portions 10-2, 10-3. More specifically, inthe high-frequency signal line 10, the signal line portions 10-2, 10-3extend from both ends of the signal line portion 10-1 toward thenegative side in the y-axis direction. On the other hand, in thehigh-frequency signal line 10 a, the signal line portion 10-2 extendsfrom an end of the signal line portion 10-1 on the negative side in thex-axis direction toward the negative side in the y-axis direction whilethe signal line portion 10-3 extends from the other end of the signalline portion 10-1 on the positive side in the x-axis direction towardthe positive side in the y-axis direction.

In the high-frequency signal line 10, in the signal line portions 10-2,10-3, the width in the x-axis direction of the connecting portions 12-2b, 12-3 b is greater than the width in the x-axis direction of the lineportions 12-2 a, 12-2 b. On the other hand, in the high-frequency signalline 10 a, the signal line portions 10-2, 10-3 preferably have a uniformor substantially uniform width in the x-axis direction. The signal lineportion 10-2 and the signal line portion 10-3 have the sameconfiguration. The other components of the high-frequency signal line 10a are the same as those of the high-frequency signal line 10, andtherefore, the description thereof is herein omitted.

Next, a non-limiting example of a manufacturing method of thehigh-frequency signal line 10 a is described. FIG. 22 is a plan view ofa mother dielectric element assembly 112 a. FIG. 23 is a plan view of amother dielectric element assembly 112 b, 112 c.

As previously described, the signal line portions 10-1 to 10-3preferably have a uniform or substantially uniform width. Therefore, asshown in FIG. 22, the signal line portions 10-1 can be formed in amatrix arrangement over the mother dielectric element assembly 112 awithout making any gaps. Likewise, as shown in FIG. 23, the signal lineportions 10-2, 10-3 can be formed in a matrix arrangement over themother dielectric element assembly 112 b, 112 c without making any gaps.With these arrangements, a larger number of signal line portions 10-1 to10-3 is obtained from the mother dielectric element assemblies 112 a to112 c. The manufacturing cost of the high-frequency signal line 10 a issignificantly reduced effectively.

Hereinafter, a high-frequency signal line according to a secondmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 24 is an explodedperspective view of a signal line portion 10-1 of a high-frequencysignal line 10 b. FIG. 25 is a cross-sectional structure view of thehigh-frequency signal line 10 b taken along line A-A. FIG. 1 and FIG. 2are referred to herein for the external perspective view and explodedperspective view of the high-frequency signal line 10 b.

The high-frequency signal line 10 b is different from the high-frequencysignal line 10 in that connecting conductors 50, 52, 54, 56 are providedand in terms of the method of joining together the signal line portions10-1 to 10-3.

The connecting conductor 50 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceS1 at the end of the dielectric element assembly 12-1 on the negativeside in the x-axis direction as shown in FIG. 24. The end of thevia-hole conductor b1 on the positive side in the z-axis direction isconnected to the connecting conductor 50. Thus, the connecting conductor50 is electrically coupled to the signal line 20-1.

The connecting conductor 52 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceS1 at the end of the dielectric element assembly 12-1 on the negativeside in the x-axis direction as shown in FIG. 24. The connectingconductor 52 is provided on the positive side in the x-axis directionrelative to the connecting conductor 50. The end of the via-holeconductor b5 on the positive side in the z-axis direction is connectedto the connecting conductor 52. Thus, the connecting conductor 52 iselectrically coupled to the reference ground conductor 22-1.

The connecting conductor 54 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceS1 at the end of the dielectric element assembly 12-1 on the positiveside in the x-axis direction as shown in FIG. 24. The end of thevia-hole conductor b3 on the positive side in the z-axis direction isconnected to the connecting conductor 54. Thus, the connecting conductor54 is electrically coupled to the signal line 20-1.

The connecting conductor 56 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceS1 at the end of the dielectric element assembly 12-1 on the positiveside in the x-axis direction as shown in FIG. 24. The connectingconductor 56 is provided on the negative side in the x-axis directionrelative to the connecting conductor 50. The end of the via-holeconductor b6 on the positive side in the z-axis direction is connectedto the connecting conductor 56. Thus, the connecting conductor 56 iselectrically coupled to the reference ground conductor 22-1.

Further, as shown in FIG. 25, the connecting conductor 50 is connectedto the connecting conductor 44 by soldering. The connecting conductor 52is connected to the connecting conductor 46 by soldering. Note that, inthe high-frequency signal line 10 b, the signal line portion 10-1 andthe signal line portion 10-2 are not welded together. Note that FIG. 25shows a small gap between the top surface S1 of the dielectric elementassembly 12-1 and the bottom surface S4 of the dielectric elementassembly 12-2 for easy understanding of provision of the solderalthough, in actuality, the top surface S1 of the dielectric elementassembly 12-1 and the bottom surface S4 of the dielectric elementassembly 12-2 are in contact with each other.

Note that the signal line portion 10-3 has a configuration of linesymmetry with respect to the signal line portion 10-2 about a lineextending in the y-axis direction so as to traverse the center in thex-axis direction of the signal line portion 10-2. The joining of thesignal line portion 10-1 and the signal line portion 10-3 is the same asthe joining of the signal line portion 10-1 and the signal line portion10-2, and therefore, the description thereof is herein omitted.

In the high-frequency signal line 10 b that has the above-describedconfiguration, the signal line portions 10-1 to 10-3 are joined togetherby soldering. Therefore, in joining the signal line portions 10-1 to10-3, compression bonding of these elements is not necessary.

Hereinafter, a high-frequency signal line according to a thirdmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 26 is an explodedperspective view of signal line portions 10-1 to 10-3 of ahigh-frequency signal line 10 c according to the third modification.FIG. 27 is an exploded perspective view of the signal line portion 10-1of the high-frequency signal line 10 c. FIG. 28 is an explodedperspective view of the signal line portion 10-2 of the high-frequencysignal line 10 c. FIG. 29 is a cross-sectional structure view of a jointportion of the signal line portion 10-1 and the signal line portion 10-2of the high-frequency signal line 10 c. FIG. 1 is referred to herein forthe external perspective view of the high-frequency signal line 10 b.

The high-frequency signal line 10 c is different from the high-frequencysignal line 10 in that the signal line portion 10-1 and the signal lineportion 10-2 are joined together by wire conductors H1, H2 as shown inFIG. 26.

The signal line portion 10-1 of the high-frequency signal line 10 cincludes connecting conductors 60 a, 60 b instead of the via-holeconductors b1 to b6 and the connecting conductors 25 a, 25 b as shown inFIG. 27. The connecting conductor 60 a is provided on a portion of thetop surface of the dielectric sheet 18-1 c at the end of the dielectricsheet 18-1 c on the negative side in the x-axis direction, and isconnected to the end of the signal line 20-1 on the negative side in thex-axis direction. The connecting conductor 60 a preferably has arectangular or substantially rectangular shape elongated in the y-axisdirection. The connecting conductor 60 b is provided on a portion of thetop surface of the dielectric sheet 18-1 c at the end of the dielectricsheet 18-1 c on the positive side in the x-axis direction, and isconnected to the end of the signal line 20-1 on the positive side in thex-axis direction. The connecting conductor 60 b preferably has arectangular or substantially rectangular shape elongated in the y-axisdirection. Each of the connecting conductors 60 a, 60 b does not overlapwith the reference ground conductor 22-1 or the auxiliary groundconductor 24-1 when viewed in plan in the z-axis direction.

The signal line portion 10-1 preferably includes marks m1 to m4. Each ofthe marks m1 to m4 preferably includes two circle marks which areprovided on the top surface of the dielectric sheet 18-1 a. The marks m1overlap with the connecting conductor 60 a when viewed in plan in thez-axis direction and are arranged in the y-axis direction. The marks m2overlap with the end of the reference ground conductor 22-1 on thenegative side in the x-axis direction when viewed in plan in the z-axisdirection and are arranged in the y-axis direction. The marks m3 overlapwith the connecting conductor 60 b when viewed in plan in the z-axisdirection and are arranged in the y-axis direction. The marks m4 overlapwith the end of the reference ground conductor 22-1 on the positive sidein the x-axis direction when viewed in plan in the z-axis direction andare arranged in the y-axis direction.

The signal line portion 10-2 of the high-frequency signal line 10 cincludes connecting conductors 62, 64, 66 instead of the via-holeconductors b9 to b13 and the connecting conductors 43 to 46. Theconnecting conductor 62 is provided on a portion of the top surface ofthe dielectric sheet 18-2 c at the end of the dielectric sheet 18-2 c onthe positive side in the y-axis direction, and is connected to the endof the signal line 20-2 on the positive side in the y-axis direction.The connecting conductor 62 preferably has a rectangular orsubstantially rectangular shape protruding from the end of the signalline 20-2 on the positive side in the y-axis direction toward thenegative side in the x-axis direction. The connecting conductor 62 doesnot overlap with the reference ground conductor 22-2 or the auxiliaryground conductor 24-2 when viewed in plan in the z-axis direction.

The connecting conductor 64 is provided on a portion of the top surfaceof the dielectric sheet 18-2 b at the end of the dielectric sheet 18-2 bon the positive side in the y-axis direction. The connecting conductor64 is connected to an end of the reference ground conductor 22-2 on thepositive side in the y-axis direction.

The connecting conductor 66 is provided on a portion of the top surfaceof the dielectric sheet 18-2 d at the end of the dielectric sheet 18-2 don the positive side in the y-axis direction. The connecting conductor66 is connected to the end of the auxiliary ground conductor 24-2 on thepositive side in the y-axis direction. The connecting conductors 64, 66overlap with each other when viewed in plan in the z-axis direction.Note that, however, the connecting conductors 64, 66 do not overlap withthe connecting conductor 62 when viewed in plan in the z-axis direction.The connecting conductors 64, 66 are positioned on the positive side inthe x-axis direction relative to the connecting conductor 62.

The signal line portion 10-2 preferably includes marks m5, m6. Each ofthe marks m5, m6 preferably includes two circle marks which are providedon the top surface of the dielectric sheet 18-2 a. The marks m5 overlapwith the connecting conductor 62 when viewed in plan in the z-axisdirection and are arranged in the y-axis direction. The marks m6 overlapwith the connecting conductors 64, 66 when viewed in plan in the z-axisdirection and are arranged in the y-axis direction.

The wire conductors H1, H2 are realized by, as shown in FIG. 26 and FIG.29, bending “

”-shaped conductors as shown in FIG. 29, and have the same configurationas staples. More specifically, the wire conductors H1, H2 include anengagement portion h1 and penetrating portions h2, h3. The penetratingportions h2, h3 extend in the z-axis direction and penetrate through thedielectric element assemblies 12-1, 12-2. The engagement portion h1extends in the x-axis direction and connects to ends of the penetratingportions h2, h3 on the positive side in the z-axis direction. The wireconductors H1, H2 are produced by bending a single wire.

The wire conductor H1 is attached to the signal line portions 10-1, 10-2so as to penetrate through the marks m1, m5. That is, the marks m1, m5indicate the attachment positions of the penetrating portions h2, h3 ofthe wire conductor H1. The penetrating portions h2, h3 of the wireconductor H1 stick into the dielectric element assemblies 12-1, 12-2 andpenetrate through the connecting conductors 60 a, 62. Thus, the signalline 20-1 and the signal line 20-2 are electrically coupled together.Leading ends of the penetrating portions h2, h3 of the wire conductor H1on the negative side in the z-axis direction are bent at the bottomsurface S2 of the dielectric element assembly 12-1. The engagementportion h1 is bent at the top surface S3 relative to the penetratingportions h1, h2. In this way, the dielectric element assembly 12-1 andthe dielectric element assembly 12-2 are joined together such that theyare not easily disengaged.

The wire conductor H2 is attached to the signal line portions 10-1, 10-2so as to penetrate through the marks m2, m6. That is, the marks m2, m6indicate the attachment positions of the penetrating portions h2, h3 ofthe wire conductor H2. The penetrating portions h2, h3 of the wireconductor H2 stick into the dielectric element assemblies 12-1, 12-2 andpenetrate through the connecting conductors 64, 66, the reference groundconductor 22-1, and the auxiliary ground conductor 24-1. Thus, thereference ground conductors 22-1, 22-2 and the auxiliary groundconductors 24-1, 24-2 are electrically coupled together. Leading ends ofthe penetrating portions h2, h3 of the wire conductor H2 on the negativeside in the z-axis direction are bent at the bottom surface S2 of thedielectric element assembly 12-1. The engagement portion h1 is bent atthe top surface S3 relative to the penetrating portions h1, h2. In thisway, the dielectric element assembly 12-1 and the dielectric elementassembly 12-2 are joined together such that they are not easilydisengaged.

Next, a non-limiting example of a manufacturing method of thehigh-frequency signal line 10 d is described. The manufacturing methodof the high-frequency signal line 10 d is different from themanufacturing method of the high-frequency signal line 10 in the step ofjoining together the top surface S1 of the signal line portion 10-1 andthe bottom surface S4 of the signal line portion 10-2. Thus, the step ofjoining together the top surface S1 of the signal line portion 10-1 andthe bottom surface S4 of the signal line portion 10-2 is now described.

First, the wire conductor H1 is stuck into the dielectric elementassembly 12-1 and the dielectric element assembly 12-2 using the marksm5 as alignment marks so as to penetrate through the connectingconductor 60 a that is electrically coupled to the signal line 20-1 andthrough the connecting conductor 62 that is electrically coupled to thesignal line 20-1. Then, the ends of the wire conductor H1 on thenegative side in the z-axis direction are bent. In this step, the wireconductor H1 is stuck so as not to penetrate through the via-holeconductors provided in the signal line portions 10-1, 10-2.

Meanwhile, the wire conductor H2 is stuck into the dielectric elementassembly 12-1 and the dielectric element assembly 12-2 using the marksm6 as alignment marks so as to penetrate through the connectingconductor 64 that is electrically coupled to the reference groundconductor 22-1, the auxiliary ground conductor 24-1, and the referenceground conductor 22-2 and through the connecting conductor 66 that iselectrically coupled to the auxiliary ground conductor 24-2. Then, theends of the wire conductor H2 on the negative side in the z-axisdirection are bent. In this step, the wire conductor H2 is stuck so asnot to penetrate through the via-hole conductors provided in the signalline portions 10-1, 10-2.

In the high-frequency signal line 10 c that has the above-describedconfiguration and the manufacturing method thereof, the wire conductorsH1, H2 enable joining of the signal line portion 10-1 and the signalline portion 10-2 and electrical coupling of the signal line 20-1 andthe signal line 20-2, and at the same time, enable electrical couplingof the reference ground conductors 22-1, 22-2 and the auxiliary groundconductors 24-1, 24-2. Thus, in the high-frequency signal line 10 c, itis not necessary to form the via-hole conductors b1, b3, b5, b6 in thesignal line portion 10-1, and compression bonding of the signal lineportion 10-1 and the signal line portion 10-2 is not necessary. That is,in the high-frequency signal line 10 c and the manufacturing methodthereof, the manufacturing process is greatly simplified.

Hereinafter, a high-frequency signal line according to a fourthmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 30 is an exploded view ofa signal line portion 10-1. FIG. 31 is an exploded view of a signal lineportion 10-2 of the high-frequency signal line 10 d. FIG. 1 is referredto herein for the external perspective view of the signal line 10 d.

The signal line 10 d is different from the high-frequency signal line 10in that the signal line 10 d has a coplanar configuration. Morespecifically, the signal line portion 10-1 of the signal line 10 d hasground conductors 122-1, 124-1 instead of the auxiliary ground conductor24-1 and the reference ground conductor 22-1 as shown in FIG. 30. Thesignal line 20-1 and the ground conductors 122-1, 124-1 are provided onthe top surface of the dielectric sheet 18-1 b so as to extend in thex-axis direction. The signal line 20-1 is provided between the groundconductors 122-1, 124-1 which are provided at the opposite sides in they-axis direction of the signal line 20-1. The ground conductor 122-1 isprovided on the positive side in the y-axis direction relative to thesignal line 20-1. The ground conductor 124-1 is provided on the negativeside in the y-axis direction relative to the signal line 20-1.

An end of the ground conductor 122-1 on the negative side in the x-axisdirection is positioned on the negative side in the x-axis directionrelative to the end of the signal line 20-1 on the negative side in thex-axis direction. The end of the signal line 20-1 on the negative sidein the x-axis direction is positioned on the negative side in the x-axisdirection relative to an end of the ground conductor 124-1 on thenegative side in the x-axis direction.

An end of the ground conductor 122-1 on the positive side in the x-axisdirection is positioned on the positive side in the x-axis directionrelative to the end of the signal line 20-1 on the positive side in thex-axis direction. The end of the signal line 20-1 on the positive sidein the x-axis direction is positioned on the positive side in the x-axisdirection relative to an end of the ground conductor 124-1 on thepositive side in the x-axis direction.

The dielectric sheet 18-1 a includes via-hole conductors b21 to b26.Ends of the via-hole conductors b21 to b23 on the positive side in thez-axis direction are exposed at a portion of the top surface S1 at theend of the dielectric element assembly 12-1 on the negative side in thex-axis direction. The other ends of the via-hole conductors b21 to b23on the negative side in the z-axis direction are respectively connectedto the ends of the signal line 20-1 and the ground conductors 122-1,124-1 on the negative side in the x-axis direction. Ends of the via-holeconductors b24 to b26 on the positive side in the z-axis direction areexposed at a portion of the top surface S1 at the end of the dielectricelement assembly 12-1 on the positive side in the x-axis direction. Theother ends of the via-hole conductors b24 to b26 on the negative side inthe z-axis direction are respectively connected to the ends of thesignal line 20-1 and the ground conductors 122-1, 124-1 on the positiveside in the x-axis direction.

In the signal line portion 10-2 of the high-frequency signal line 10 d,a signal line 20-2 and ground conductors 122-2, 124-2 are provided onthe top surface of the dielectric sheet 18-2 b so as to extend in they-axis direction as shown in FIG. 31. The signal line 20-2 is providedbetween the ground conductors 122-2, 124-2 which are provided at theopposite sides in the x-axis direction of the signal line 20-2.

An end of the ground conductor 122-2 on the positive side in the y-axisdirection is positioned on the positive side in the y-axis directionrelative to the end of the signal line 20-2 on the positive side in they-axis direction. The end of the signal line 20-2 on the positive sidein the y-axis direction is positioned on the positive side in the y-axisdirection relative to an end of the ground conductor 124-2 on thepositive side in the y-axis direction.

The bottom surface of the dielectric sheet 18-2 b is provided withconnecting conductors 70, 72, 74. The connecting conductor 70 overlapswith the end of the signal line 20-2 on the positive side in the y-axisdirection when viewed in plan in the z-axis direction. The connectingconductor 72 overlaps with the end of the ground conductor 122-2 on thepositive side in the y-axis direction when viewed in plan in the z-axisdirection. The connecting conductor 74 overlaps with the end of theground conductor 124-2 on the positive side in the y-axis direction whenviewed in plan in the z-axis direction.

The dielectric sheet 18-2 b includes via-hole conductors b31 to b33. Thevia-hole conductor b31 connects the end of the signal line 20-2 on thepositive side in the y-axis direction to the connecting conductor 70.The via-hole conductor b32 connects the end of the ground conductor122-2 on the positive side in the y-axis direction to the connectingconductor 72. The via-hole conductor b33 connects the end of the groundconductor 124-2 on the positive side in the y-axis direction to theconnecting conductor 74.

The signal line portion 10-1 and the signal line portion 10-2 of thehigh-frequency signal line 10 d are welded together in the same way asthe signal line portion 10-1 and the signal line portion 10-2 of thehigh-frequency signal line 10 a. The via-hole conductors b21 to b23 arerespectively connected to the connecting conductors 70, 72, 74. In thisway, the signal line portion 10-1 and the signal line portion 10-2 arejoined together. Note that the signal line portion 10-3 has aconfiguration of line symmetry with respect to the signal line portion10-2 about a line extending in the y-axis direction so as to traversethe center in the x-axis direction of the signal line portion 10-2.

Hereinafter, a high-frequency signal line according to a fifthmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 32 is an externalperspective view of a high-frequency signal line 10 e according to thefifth modification. FIG. 33A is an exploded view of a signal lineportion 10-1 of the high-frequency signal line 10 e. FIG. 33B is across-sectional structure view of the signal line portion 10-1 of thehigh-frequency signal line 10 e. FIG. 34 is a plan view of an end of thesignal line portion 10-1 on the negative side in the x-axis direction.FIG. 35A is an exploded view of a signal line portion 10-2 of thehigh-frequency signal line 10 e. FIG. 35B is a cross-sectional structureview of the signal line portion 10-2 of the high-frequency signal line10 e. FIG. 36 is a plan view of an end of the signal line portion 10-2on the negative side in the y-axis direction. FIG. 37 is across-sectional structure view of the high-frequency signal line 10 e ofFIG. 32 taken along line A-A.

The high-frequency signal line 10 e includes signal line portions 10-1to 10-3 as shown in FIG. 32.

The signal line portion 10-1 is formed preferably by laminating a resistlayer 17-1 and dielectric sheets 18-1 a to 18-1 d as shown in FIG. 33A.The resist layer 17-1 is a resin layer. The top surface of thedielectric sheet 18-1 b is provided with a reference ground conductor22-1. The top surface of the dielectric sheet 18-1 c is provided with asignal line 20-1 and connecting conductors 80 a, 80 b. The top surfaceof the dielectric sheet 18-1 d is provided with an auxiliary groundconductor 24-1. The signal line 20-1, the reference ground conductor22-1, and the auxiliary ground conductor 24-1 of the high-frequencysignal line 10 e have the same configuration as the signal line 20-1,the reference ground conductor 22-1, and the auxiliary ground conductor24-1 of the high-frequency signal line 10, and therefore, thedescription thereof is herein omitted. The connecting conductor 80 apreferably is a rectangular or substantially rectangular conductor andis provided on the negative side in the x-axis direction relative to thesignal line 20-1. The connecting conductor 80 b preferably is arectangular or substantially rectangular conductor and is provided onthe positive side in the x-axis direction relative to the signal line20-1.

The via-hole conductors B1-1, B3-1 pierce through the dielectric sheet18-1 b in the z-axis direction. The via-hole conductors B2-1, B4-1pierce through the dielectric sheet 18-1 c in the z-axis direction. Thevia-hole conductors B1-1, B2-1 are connected to each other, such thatthe reference ground conductor 22-1 and the auxiliary ground conductor24-1 are connected to each other. The via-hole conductors B3-1, B4-1 areconnected to each other, such that the reference ground conductor 22-1and the auxiliary ground conductor 24-1 are connected to each other.

The via-hole conductors b40, b41 pierce through the dielectric sheet18-1 c in the z-axis direction. The via-hole conductor b40 connects theconnecting conductor 80 a to the auxiliary ground conductor 24-1. Thevia-hole conductor b41 connects the connecting conductor 80 b to theauxiliary ground conductor 24-1.

In the signal line portion 10-1, the length in the x-axis direction ofthe dielectric sheets 18-1 a, 18-1 b is smaller than the length in thex-axis direction of the dielectric sheets 18-1 c, 18-1 d. Thus, as shownin FIG. 33B, the top surface of parts of the signal line portion 10-1near the opposite ends in the x-axis direction of the signal lineportion 10-1 has a step so that the thickness of the parts of the signalline portion 10-1 near the opposite ends in the x-axis direction of thesignal line portion 10-1 is smaller than the thickness of the remaininga portion the signal line portion 10-1. Further, near the opposite endsof the signal line portion 10-1, the opposite ends of the signal line20-1 and the connecting conductors 80 a, 80 b are exposed as shown inFIG. 34.

The signal line portion 10-2 is formed preferably by laminating a resistlayer 17-2 and dielectric sheets 18-2 a to 18-2 d as shown in FIG. 35A.The top surface of the dielectric sheet 18-2 a is provided with areference ground conductor 22-2 and a connecting conductor 81. The topsurface of the dielectric sheet 18-2 b is provided with a signal line20-2. The top surface of the dielectric sheet 18-2 c is provided with anauxiliary ground conductor 24-2. The signal line 20-2, the referenceground conductor 22-2, and the auxiliary ground conductor 24-2 of thehigh-frequency signal line 10 e have the same configuration as thesignal line 20-2, the reference ground conductor 22-2, and the auxiliaryground conductor 24-2 of the high-frequency signal line 10, andtherefore, the description thereof is herein omitted. The connectingconductor 81 preferably is a rectangular or substantially rectangularconductor and is surrounded by the terminal portion 22-2 b of thereference ground conductor 22-1.

The via-hole conductors B1-2, B3-2 pierce through the dielectric sheet18-2 a in the z-axis direction. The via-hole conductors B2-2, B4-2pierce through the dielectric sheet 18-2 b in the z-axis direction. Thevia-hole conductors B1-2, B2-2 are connected to each other, such thatthe reference ground conductor 22-2 and the auxiliary ground conductor24-2 are connected to each other. The via-hole conductors B3-2, B4-2 areconnected to each other, such that the reference ground conductor 22-2and the auxiliary ground conductor 24-2 are connected to each other.

The via-hole conductor b8 pierces through the dielectric sheet 18-2 a inthe z-axis direction so as to connect the end of the signal line 20-2 onthe negative side in the y-axis direction to the connecting conductor81.

The resist layer 17-2 is a resin layer for protection of the referenceground conductor 22-2. The resist layer 17-2 includes openings Ha to Hd.The connecting conductor 81 is exposed to the outside through theopening Ha. The terminal portion 22-2 b is exposed to the outsidethrough the openings Hb to Hd and therefore functions as an externalterminal.

In the signal line portion 10-2, the length in the x-axis direction ofthe dielectric sheets 18-2 c, 18-2 d is smaller than the length in they-axis direction of the resist layer 17-2 and the dielectric sheets 18-2a, 18-2 b. Thus, as shown in FIG. 35B, the bottom surface of a portionthe signal line portion 10-2 near the end of the signal line portion10-2 on the positive side in the y-axis direction has a step so that thethickness of a portion the signal line portion 10-2 near the end of thesignal line portion 10-2 on the positive side in the y-axis direction issmaller than the thickness of the remaining a portion the signal lineportion 10-2. Further, near the end of the signal line portion 10-2 onthe positive side in the y-axis direction, the via-hole conductors b9,b12 are exposed as shown in FIG. 36.

The signal line portions 10-1, 10-2, 10-3 that have the above-describedconfiguration are joined together to provide a single high-frequencysignal line 10 e as shown in FIG. 32. More specifically, as shown inFIG. 32, a portion of the top surface S1 at the end of the dielectricelement assembly 12-1 on the negative side in the x-axis direction and aportion of the bottom surface S4 at the end of the dielectric elementassembly 12-2 on the positive side in the y-axis direction are joinedtogether. In the present preferred embodiment, a portion of the topsurface S1 at the end of the dielectric element assembly 12-1 on thenegative side in the x-axis direction and a portion of the bottomsurface S4 at the end of the dielectric element assembly 12-2 on thepositive side in the y-axis direction are welded together. In this step,as shown in FIG. 37, the smaller thickness portion of the signal lineportion 10-1 and the smaller thickness portion of the signal lineportion 10-2 are placed one on the other. Thus, the signal line portion10-1 and the signal line portion 10-2 are joined together, and the jointportion of the dielectric element assembly 12-1 and the dielectricelement assembly 12-2 includes a corner (a bent portion which is bent ina planar direction of the high-frequency signal line 10 e).

Further, as shown in FIG. 37, the end of the signal line 20-1 on thenegative side in the x-axis direction is connected to the via-holeconductor b12. Thus, the signal line 20-1 and the signal line 20-2 areelectrically coupled together. The connecting conductor 80 a isconnected to the via-hole conductor b9. Thus, the reference groundconductors 22-1, 22-2 and the auxiliary ground conductors 24-1, 24-2 areelectrically coupled together.

Note that the signal line portion 10-3 has a configuration of linesymmetry with respect to the signal line portion 10-2 about a lineextending in the y-axis direction so as to traverse the center in thex-axis direction of the signal line portion 10-2, and therefore, thedescription thereof is herein omitted.

In the high-frequency signal line 10 e that has the above-describedconfiguration, the smaller thickness portion of the signal line portion10-1 and the smaller thickness portion of the signal line portion 10-2are placed one on the other. Therefore, the signal line portion 10-1fits in the step of the signal line portion 10-2, and the signal lineportion 10-2 fits in the step of the signal line portion 10-1. Thus, thesignal line portion 10-1 and the signal line portion 10-2 are properlyaligned. As a result, in the high-frequency signal line 10 e, occurrenceof disconnection which is attributed to dislocation of the signal lineportion 10-1 and the signal line portion 10-2 is prevented. Further,alignment in the joining step is easy, and therefore, the step ofjoining together the signal line portions 10-1, 10-2, 10-3 is also easy.

In the high-frequency signal line 10 e, the thickness of the jointportion of the signal line portion 10-1 and the signal line portion 10-2is significantly reduced. Particularly when the signal line portions10-1, 10-2, 10-3 are joined together to form the high-frequency signalline 10 e, it is preferred that the high-frequency signal line 10 e isconfigured to have no steps in the top and bottom surfaces.

Hereinafter, a high-frequency signal line according to a sixthmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 38 is a perspective viewof an electronic device 200 including a high-frequency signal line 10 f.FIG. 39 is an exploded view of a signal line portion 10-1 of thehigh-frequency signal line 10 f. FIG. 40 is an exploded view of a signalline portion 10-2 of the high-frequency signal line 10 f.

As shown in FIG. 38, the high-frequency signal line 10 f may sometimesbe bent near the joint portion of the signal line portion 10-1 and thesignal line portion 10-2 and the joint portion of the signal lineportion 10-1 and the signal line portion 10-3. In this case, in thehigh-frequency signal line 10 b, force effects on these joint portions,and therefore, there is a probability that disconnection occurs betweenthe signal line portion 10-1 and the signal line portion 10-2 andbetween the signal line portion 10-1 and the signal line portion 10-3.

In view of such circumstances, the signal line portion 10-1 of thehigh-frequency signal line 10 f includes dummy conductors 90 a to 90 c,91 a to 91 c in addition to the components of the signal line portion10-1 of the high-frequency signal line 10 b. The signal line portion10-2 of the high-frequency signal line 10 f includes dummy conductors 92a to 92 c in addition to the components of the signal line portion 10-1of the high-frequency signal line 10 b.

The dummy conductors 90 a to 90 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of the topsurface of the dielectric sheet 18-1 a near the end of the dielectricsheet 18-1 a on the negative side in the x-axis direction. Morespecifically, the dummy conductors 90 a, 90 b are provided on the topsurface of the dielectric sheet 18-1 a so as to be arranged along thelong side of the dielectric sheet 18-1 a on the positive side in they-axis direction. The dummy conductor 90 c is provided on a portion ofthe top surface of the dielectric sheet 18-1 a near the short side ofthe dielectric sheet 18-1 a on the negative side in the x-axisdirection. That is, the dummy conductors 90 a to 90 c are provided onthe negative side in the x-axis direction and on the positive side inthe y-axis direction relative to the via-hole conductors b1, b5, i.e.,in two directions from the via-hole conductors b1, b5.

The dummy conductors 91 a to 91 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of the topsurface of the dielectric sheet 18-1 a near the end of the dielectricsheet 18-1 a on the positive side in the x-axis direction. Morespecifically, the dummy conductors 91 a, 91 b are provided on the topsurface of the dielectric sheet 18-1 a so as to be arranged along thelong side of the dielectric sheet 18-1 a on the positive side in they-axis direction. The dummy conductor 91 c is provided on a portion ofthe top surface of the dielectric sheet 18-1 a near the short side ofthe dielectric sheet 18-1 a on the positive side in the x-axisdirection. That is, the dummy conductors 91 a to 91 c are provided onthe positive side in the x-axis direction and on the positive side inthe y-axis direction relative to the via-hole conductors b3, b6, i.e.,in two directions from the via-hole conductors b3, b6.

The dummy conductors 92 a to 92 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of thebottom surface of the dielectric sheet 18-2 d near the end of thedielectric sheet 18-2 d on the positive side in the y-axis direction.More specifically, the dummy conductors 92 a, 92 b are provided on thebottom surface of the dielectric sheet 18-2 d so as to be arranged alongthe short side of the dielectric sheet 18-2 d on the positive side inthe y-axis direction. The dummy conductor 92 c is provided on a portionof the bottom surface of the dielectric sheet 18-2 d near the short sideof the dielectric sheet 18-2 d on the negative side in the x-axisdirection. That is, the dummy conductors 92 a to 92 c are provided onthe negative side in the x-axis direction and on the positive side inthe y-axis direction relative to the connecting conductors 44, 46, i.e.,in two directions from the connecting conductors 44, 46.

Corners of the signal line portions 10-1, 10-2 which are on the negativeside in the x-axis direction and which are on the positive side in they-axis direction are rounded. These rounded corners facilitate alignmentof the signal line portion 10-1 and the signal line portion 10-2.

When the signal line portion 10-1 and the signal line portion 10-2 thathave the above-described configuration are joined together, the dummyconductor 90 a and the dummy conductor 92 a are connected together via asolder, the dummy conductor 90 b and the dummy conductor 92 b areconnected together via a solder, and the dummy conductor 90 c and thedummy conductor 92 c are connected together via a solder. Note that thesignal line portion 10-3 has a configuration of line symmetry withrespect to the signal line portion 10-2 about a line extending in they-axis direction so as to traverse the center in the x-axis direction ofthe signal line portion 10-2, and therefore, the description thereof isherein omitted. The other components of the high-frequency signal line10 f are the same as those of the high-frequency signal line 10 b, andtherefore, the description thereof is herein omitted.

According to the high-frequency signal line 10 f that has theabove-described configuration, the dummy conductors 90 a to 90 c and thedummy conductors 92 a to 92 c are connected together via a solder.Therefore, the signal line portion 10-1 and the signal line portion 10-2are strongly secured together. As a result, the signal line portion 10-1and the signal line portion 10-2 are prevented from being easilydisconnected.

In the high-frequency signal line 10 f, an antenna may be provided nearthe high-frequency signal line 10 f as shown in FIG. 38, and even inthis case, the characteristics of the antenna are unlikely to vary. Morespecifically, a possible way of strongly securing the signal lineportion 10-1 and the signal line portion 10-2 is to increase the size ofthe connecting conductors 44, 46, for example. However, the connectingconductors 44, 46 are respectively connected to the signal line 20-2 andthe reference ground conductors 22-2, 24-2. Thus, the characteristicimpedance of the high-frequency signal line 10 f can deviate from apredetermined characteristic impedance, or variation can occur in thecharacteristics of the antenna.

In view of such circumstances, in the high-frequency signal line 10 f,the dummy conductors 90 a to 90 c, 91 a to 91 c are connected bysoldering. The dummy conductors 90 a to 90 c, 91 a to 91 c are floatingconductors that are not connected to any other conductor. Therefore,even when the dummy conductors 90 a to 90 c, 91 a to 91 c are provided,the characteristic impedance of the high-frequency signal line 10 f isunlikely to deviate from a predetermined characteristic impedance, andvariation is unlikely to occur in the characteristics of the antenna.

Hereinafter, a high-frequency signal line according to a seventhmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 41 is an exploded view ofa signal line portion 10-1 of a high-frequency signal line 10 g. FIG. 42is a cross-sectional structure view of the signal line portion 10-1 ofthe high-frequency signal line 10 g. FIG. 43 is a plan view of an end ofthe signal line portion 10-1 on the negative side in the x-axisdirection. FIG. 44 is an exploded view of a signal line portion 10-2 ofthe high-frequency signal line 10 g. FIG. 45 is a cross-sectionalstructure view of the signal line portion 10-2 of the high-frequencysignal line 10 g. FIG. 46 is a plan view of an end of the signal lineportion 10-2 on the negative side in the y-axis direction. FIG. 47 is across-sectional structure view of the high-frequency signal line 10 g ofFIG. 32 taken along line A-A. FIG. 32 is referred to herein for theexternal perspective view of the high-frequency signal line 10 g.

The high-frequency signal line 10 g includes signal line portions 10-1to 10-3 as shown in FIG. 32.

The signal line portion 10-1 is formed preferably by laminating a resistlayer 17-1 and dielectric sheets 18-1 a to 18-1 e as shown in FIG. 41.The resist layer 17-1 is a resin layer. The top surface of thedielectric sheet 18-1 b is provided with a reference ground conductor22-1. The bottom surface of the dielectric sheet 18-1 c is provided witha signal line 20-1 and connecting conductors 80 a, 80 b. The bottomsurface of the dielectric sheet 18-1 d is provided with an auxiliaryground conductor 24-1. The signal line 20-1, the reference groundconductor 22-1, and the auxiliary ground conductor 24-1 of thehigh-frequency signal line 10 g have the same configuration as thesignal line 20-1, the reference ground conductor 22-1, and the auxiliaryground conductor 24-1 of the high-frequency signal line 10, andtherefore, the description thereof is herein omitted. The connectingconductor 80 a preferably is a rectangular or substantially rectangularconductor and is provided on the negative side in the x-axis directionrelative to the signal line 20-1. The connecting conductor 80 bpreferably is a rectangular or substantially rectangular conductor andis provided on the positive side in the x-axis direction relative to thesignal line 20-1.

The via-hole conductors B2-1, B4-1 pierce through the dielectric sheet18-1 c in the z-axis direction and connect the reference groundconductor 22-1 to the auxiliary ground conductor 24-1.

The via-hole conductors b40, b41 pierce through the dielectric sheet18-1 c in the z-axis direction. An end of the via-hole conductor b40 onthe negative side in the z-axis direction is connected to the connectingconductor 80 a. An end of the via-hole conductor b41 on the negativeside in the z-axis direction is connected to the connecting conductor 80b.

The via-hole conductors b42, b43 pierce through the dielectric sheet18-1 d in the z-axis direction. The via-hole conductor b42 connects theconnecting conductor 80 a to the auxiliary ground conductor 24-1. Thevia-hole conductor b43 connects the connecting conductor 80 b to theauxiliary ground conductor 24-1.

The via-hole conductors b44, b45 pierce through the dielectric sheet18-1 c in the z-axis direction. An end of the via-hole conductor b44 onthe negative side in the z-axis direction is connected to the end of thesignal line 20-1 on the negative side in the x-axis direction. An end ofthe via-hole conductor b45 on the negative side in the z-axis directionis connected to the other end of the signal line 20-1 on the positiveside in the x-axis direction.

In the signal line portion 10-1, the length in the x-axis direction ofthe dielectric sheets 18-1 a, 18-1 b is smaller than the length in thex-axis direction of the dielectric sheets 18-1 c to 18-1 e. Thus, asshown in FIG. 42, portions of the signal line portion 10-1 near theopposite ends in the x-axis direction of the signal line portion 10-1have steps so that the thickness of the portions of the signal lineportion 10-1 near the opposite ends in the x-axis direction of thesignal line portion 10-1 is smaller than the thickness of the remaininga portion the signal line portion 10-1. Further, the via-hole conductorsb40, b44 are exposed at portions of the top surface of the signal lineportion 10-1 near the opposite ends of the signal line portion 10-1 asshown in FIG. 43.

The signal line portion 10-2 is formed preferably by laminating a resistlayer 17-2 and dielectric sheets 18-2 a to 18-2 e as shown in FIG. 44.The top surface of the dielectric sheet 18-2 a is provided with areference ground conductor 22-2 and a connecting conductor 81. The topsurface of the dielectric sheet 18-2 b is provided with a signal line20-2. The top surface of the dielectric sheet 18-2 c is provided with anauxiliary ground conductor 24-2. The signal line 20-2, the referenceground conductor 22-2, and the auxiliary ground conductor 24-2 of thehigh-frequency signal line 10 g have the same configuration as thesignal line 20-2, the reference ground conductor 22-2, and the auxiliaryground conductor 24-2 of the high-frequency signal line 10, andtherefore, the description thereof is herein omitted. The connectingconductor 81 preferably is a rectangular or substantially rectangularconductor and is surrounded by the terminal portion 22-2 b of thereference ground conductor 22-1.

The via-hole conductors B1-2, B3-2 pierce through the dielectric sheet18-2 a in the z-axis direction. The via-hole conductors B2-2, B4-2pierce through the dielectric sheet 18-2 b in the z-axis direction. Thevia-hole conductors B1-2, B2-2 are connected to each other, such thatthe reference ground conductor 22-2 and the auxiliary ground conductor24-2 are connected to each other. The via-hole conductors B3-2, B4-2 areconnected to each other, such that the reference ground conductor 22-2and the auxiliary ground conductor 24-2 are connected to each other.

The via-hole conductor b8 pierces through the dielectric sheet 18-2 a inthe z-axis direction so as to connect an end of the signal line 20-1 onthe negative side in the y-axis direction to the connecting conductor81.

The resist layer 17-2 is a resin layer for protection of the referenceground conductor 22-2. The resist layer 17-2 has openings Ha to Hd. Theconnecting conductor 81 is exposed to the outside through the openingHa. The terminal portion 22-2 b is exposed to the outside through theopenings Hb to Hd and therefore functions as an external terminal.

In the signal line portion 10-2, the length in the x-axis direction ofthe dielectric sheets 18-2 c, 18-2 d is smaller than the length in they-axis direction of the resist layer 17-2 and the dielectric sheets 18-2a, 18-2 b. Thus, as shown in FIG. 45, a portion the signal line portion10-2 near the end of the signal line portion 10-2 on the positive sidein the y-axis direction has a step so that the thickness of the portionof the signal line portion 10-2 near the end of the signal line portion10-2 on the positive side in the y-axis direction is smaller than thethickness of the remaining portion of the signal line portion 10-2.Further, the via-hole conductors b9, b12 are exposed at a portion of thebottom surface of the signal line portion 10-2 near the end of thesignal line portion 10-2 on the positive side in the y-axis direction asshown in FIG. 46.

The signal line portions 10-1, 10-2 that have the above-describedconfiguration are joined together to define a single high-frequencysignal line 10 g as shown in FIG. 32. More specifically, as shown inFIG. 32, a portion of the top surface S1 at the end of the dielectricelement assembly 12-1 on the negative side in the x-axis direction and aportion of the bottom surface S4 at the end of the dielectric elementassembly 12-2 on the positive side in the y-axis direction are joinedtogether. In the present preferred embodiment, a portion of the topsurface S1 at the end of the dielectric element assembly 12-1 on thenegative side in the x-axis direction and a portion of the bottomsurface S4 at the end of the dielectric element assembly 12-2 on thepositive side in the y-axis direction are welded together. In this step,as shown in FIG. 47, the smaller thickness portion of the signal lineportion 10-1 and the smaller thickness portion of the signal lineportion 10-2 are placed one on the other. Thus, the signal line portion10-1 and the signal line portion 10-2 are joined together, and the jointportion of the dielectric element assembly 12-1 and the dielectricelement assembly 12-2 includes a corner (a bent portion which is bent ina planar direction of the high-frequency signal line 10 g).

Further, as shown in FIG. 47, the via-hole conductor b12 and thevia-hole conductor b44 are connected to each other. Thus, the signalline 20-1 and the signal line 20-2 are electrically coupled together.Meanwhile, the via-hole conductor b9 and the via-hole conductor b40 areconnected to each other. Thus, the reference ground conductors 22-1,22-2 and the auxiliary ground conductors 24-1, 24-2 are electricallycoupled together.

Note that the signal line portion 10-3 has the same configuration as thesignal line portion 10-2, and therefore, the description thereof isherein omitted.

In the high-frequency signal line 10 g that has the above-describedconfiguration, occurrence of disconnection which is attributed todislocation of the signal line portion 10-1 and the signal line portion10-2 is prevented as in the high-frequency signal line 10 e.

In the high-frequency signal line 10 g, the thickness of the jointportion of the signal line portion 10-1 and the signal line portion 10-2is significantly reduced as in the high-frequency signal line 10 e.

In the high-frequency signal line 10 g, the signal line portion 10-1 andthe signal line portion 10-2 are joined more strongly than in thehigh-frequency signal line 10 e. More specifically, as shown in FIG. 37,in the high-frequency signal line 10 e, the via-hole conductor b9 andthe connecting conductor 80 a are connected together, and the via-holeconductor b12 and the signal line 20-1 are connected together. In thiscase, a portion of the connecting conductor 80 a spreading out of thevia-hole conductor b9 and a portion the signal line 20-1 spreading outof the via-hole conductor b12 are in contact with the bottom surface ofthe dielectric sheet 18-2 c of the signal line portion 10-2. Therefore,in these portions, the dielectric sheets are not welded together.

On the other hand, in the high-frequency signal line 10 g, the via-holeconductor b9 and the via-hole conductor b40 are connected together, andthe via-hole conductor b12 and the via-hole conductor b44 are connectedtogether. Therefore, the connecting surface of the signal line portion10-1 and the signal line portion 10-2 does not include a conductor, suchas the signal line 20-1. Thus, in portions of the high-frequency signalline 10 g exclusive of the via-hole conductors b9, b12, b40, b44, thedielectric sheets are welded together. As a result, in thehigh-frequency signal line 10 g, the signal line portion 10-1 and thesignal line portion 10-2 are joined more strongly than in thehigh-frequency signal line 10 e.

Hereinafter, a high-frequency signal line according to an eighthmodification of a preferred embodiment of the present invention isdescribed with reference to the drawings. FIG. 48 is an exploded view ofa signal line portion 10-1 of a high-frequency signal line 10 h. FIG. 49is an exploded view of a signal line portion 10-2 of the high-frequencysignal line 10 h. FIG. 1 is referred to herein for the externalperspective view of the high-frequency signal line 10 h.

In the high-frequency signal line 10 h, the dielectric elementassemblies 12-1 to 12-3 are joined more strongly than in thehigh-frequency signal line 10 f. The following description of thehigh-frequency signal line 10 h is mainly focused on the differencesfrom the high-frequency signal line 10 f. Note that description ofcomponents of the high-frequency signal line 10 h which are the same asthose of the high-frequency signal line 10 f is herein omitted.

In the signal line portion 10-1 of the high-frequency signal line 10 h,the reference ground conductor 22-1, the connecting conductors 50, 52,54, 56, and the dummy conductors 90 a to 90 c, 91 a to 91 c are providedon the top surface of the dielectric sheet 18-1 a. The signal line 20-1is provided on the top surface of the dielectric sheet 18-1 c. Theauxiliary ground conductor 24-1 is provided on the top surface of thedielectric sheet 18-1 d.

The configurations of the reference ground conductor 22-1, the signalline 20-1, and the auxiliary ground conductor 24-1 are the same as thoseof the reference ground conductor 22-1, the signal line 20-1, and theauxiliary ground conductor 24-1 of the high-frequency signal line 10 f.

The connecting conductor 50 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceof the dielectric sheet 18-1 a at the end of the dielectric sheet 18-1 aon the negative side in the x-axis direction. The connecting conductor52 preferably is a rectangular or substantially rectangular conductorwhich is provided on a portion of the top surface of the dielectricsheet 18-1 a at the end of the dielectric sheet 18-1 a on the negativeside in the x-axis direction, at a position on the positive side in thex-axis direction relative to the connecting conductor 50.

The connecting conductor 54 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the top surfaceof the dielectric sheet 18-1 a at the end of the dielectric sheet 18-1 aon the positive side in the x-axis direction. The connecting conductor56 preferably is a rectangular or substantially rectangular conductorwhich is provided on a portion of the top surface of the dielectricsheet 18-1 a at the end of the dielectric sheet 18-1 a on the positiveside in the x-axis direction, at a position on the negative side in thex-axis direction relative to the connecting conductor 54. The connectingconductors 52, 56 are connected to the reference ground conductor 22-1at the top surface of the dielectric sheet 18-1 a.

The dummy conductors 90 a to 90 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of the topsurface of the dielectric sheet 18-1 a near the end of the dielectricsheet 18-1 a on the negative side in the x-axis direction. Morespecifically, the dummy conductors 90 a, 90 b are provided on the topsurface of the dielectric sheet 18-1 a so as to be arranged along thelong side of the dielectric sheet 18-1 a on the positive side in they-axis direction. The dummy conductor 90 c is provided on a portion ofthe top surface of the dielectric sheet 18-1 a near the short side ofthe dielectric sheet 18-1 a on the negative side in the x-axisdirection.

The dummy conductors 91 a to 91 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of the topsurface of the dielectric sheet 18-1 a near the end of the dielectricsheet 18-1 a on the positive side in the x-axis direction. Morespecifically, the dummy conductors 91 a, 91 b are provided on the topsurface of the dielectric sheet 18-1 a so as to be arranged along thelong side of the dielectric sheet 18-1 a on the positive side in they-axis direction. The dummy conductor 91 c is provided on a portion ofthe top surface of the dielectric sheet 18-1 a near the short side ofthe dielectric sheet 18-1 a on the positive side in the x-axisdirection.

The signal line portion 10-1 of the high-frequency signal line 10 hincludes dummy conductors 93 a to 93 c, 94 a to 94 c, connectingconductors 96, 97, and via-hole conductors b51 to b56 in addition to thecomponents of the signal line portion 10-1 of the high-frequency signalline 10 f.

The dummy conductors 93 a to 93 c preferably have a rectangular orsubstantially rectangular shape and are provided in the dielectricelement assembly 12-1. The dummy conductors 93 a to 93 c are provided ona portion of the top surface of the dielectric sheet 18-1 b near the endof the dielectric sheet 18-1 b on the negative side in the x-axisdirection. More specifically, the dummy conductors 93 a, 93 b areprovided on the top surface of the dielectric sheet 18-1 b so as to bearranged along the long side of the dielectric sheet 18-1 b on thepositive side in the y-axis direction. Thus, the dummy conductors 93 a,93 b overlap with the dummy conductors 90 a, 90 b when viewed in plan inthe z-axis direction. The dummy conductor 93 c is provided on a portionof the top surface of the dielectric sheet 18-1 b near the short side ofthe dielectric sheet 18-1 b on the negative side in the x-axisdirection. Thus, the dummy conductor 93 c overlaps with the dummyconductor 90 c when viewed in plan in the z-axis direction.

The dummy conductors 94 a to 94 c preferably have a rectangular orsubstantially rectangular shape and are provided in the dielectricelement assembly 12-1. The dummy conductors 94 a to 94 c are provided ona portion of the top surface of the dielectric sheet 18-1 b near the endof the dielectric sheet 18-1 b on the positive side in the x-axisdirection. More specifically, the dummy conductors 94 a, 94 b areprovided on the top surface of the dielectric sheet 18-1 b so as to bearranged along the long side of the dielectric sheet 18-1 b on thepositive side in the y-axis direction. Thus, the dummy conductors 94 a,94 b overlap with the dummy conductors 91 a, 91 b when viewed in plan inthe z-axis direction. The dummy conductor 94 c is provided on a portionof the top surface of the dielectric sheet 18-1 b near the short side ofthe dielectric sheet 18-1 b on the positive side in the x-axisdirection. Thus, the dummy conductor 94 c overlaps with the dummyconductor 91 c when viewed in plan in the z-axis direction.

The connecting conductor 96 preferably has a rectangular orsubstantially rectangular shape and is provided on a portion of the topsurface of the dielectric sheet 18-1 b near the end of the dielectricsheet 18-1 b on the negative side in the x-axis direction. Thus, theconnecting conductor 96 overlaps with the connecting conductor 50 whenviewed in plan in the z-axis direction.

The connecting conductor 97 preferably has a rectangular orsubstantially rectangular shape and is provided on a portion of the topsurface of the dielectric sheet 18-1 b near the end of the dielectricsheet 18-1 b on the positive side in the x-axis direction. Thus, theconnecting conductor 97 overlaps with the connecting conductor 54 whenviewed in plan in the z-axis direction.

The via-hole conductors b51 to b56 pierce through the dielectric sheet18-1 a in the z-axis direction. The via-hole conductor b51 connects thedummy conductor 90 a to the dummy conductor 93 a. The via-hole conductorb52 connects the dummy conductor 90 b to the dummy conductor 93 b. Thevia-hole conductor b53 connects the dummy conductor 90 c to the dummyconductor 93 c. The via-hole conductor b54 connects the dummy conductor91 a to the dummy conductor 94 a. The via-hole conductor b55 connectsthe dummy conductor 91 b to the dummy conductor 94 b. The via-holeconductor b56 connects the dummy conductor 91 c to the dummy conductor94 c.

In the signal line portion 10-1, the resist layer 17-1 is provided onthe top surface of the dielectric sheet 18-1 a so as to cover thereference ground conductor 22-1. Note that, however, the connectingconductors 50, 52, 54, 56 and the dummy conductors 90 a to 90 c, 91 a to91 c are not covered with the resist layer 17-1.

In the signal line portion 10-2 of the high-frequency signal line 10 h,the external terminals 16-1 a to 16-1 d are provided on the top surfaceof the dielectric sheet 18-2 a, and the reference ground conductor 22-2is provided on the bottom surface of the dielectric sheet 18-2 a. Thesignal line 20-2 is provided on the bottom surface of the dielectricsheet 18-2 c. The auxiliary ground conductor 24-2, the connectingconductors 44, 46, the dummy conductors 92 a to 92 c are provided on thebottom surface of the dielectric sheet 18-2 d.

The configurations of the reference ground conductor 22-2, the signalline 20-2, and the auxiliary ground conductor 24-2 are the same as thoseof the reference ground conductor 22-2, the signal line 20-2, and theauxiliary ground conductor 24-2 of the high-frequency signal line 10 f.

The connecting conductor 44 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the bottomsurface of the dielectric sheet 18-2 d at the end of the dielectricsheet 18-2 d on the positive side in the y-axis direction. Theconnecting conductor 46 preferably is a rectangular or substantiallyrectangular conductor which is provided on a portion of the bottomsurface of the dielectric sheet 18-2 d at the end of the dielectricsheet 18-2 d on the positive side in the y-axis direction, at a positionon the positive side in the x-axis direction relative to the connectingconductor 44. The connecting conductor 46 is connected to the auxiliaryground conductor 24-2 at the bottom surface of the dielectric sheet 18-2d.

The dummy conductors 92 a to 92 c preferably have a rectangular orsubstantially rectangular shape and are provided on a portion of thebottom surface of the dielectric sheet 18-2 d near the end of thedielectric sheet 18-2 d on the positive side in the y-axis direction.More specifically, the dummy conductors 92 a, 92 b are provided on thebottom surface of the dielectric sheet 18-2 d so as to be arranged alongthe short side of the dielectric sheet 18-2 d on the positive side inthe y-axis direction. The dummy conductor 92 c is provided on a portionof the bottom surface of the dielectric sheet 18-2 d near the long sideof the dielectric sheet 18-2 d on the negative side in the x-axisdirection.

The signal line portion 10-2 of the high-frequency signal line 10 hincludes dummy conductors 95 a to 95 c, connecting conductors 98, 99,and via-hole conductors b57 to b59, b8′ in addition to the components ofthe signal line portion 10-1 of the high-frequency signal line 10 f.

The dummy conductors 95 a to 95 c preferably have a rectangular orsubstantially rectangular shape and are provided in the dielectricelement assembly 12-2. The dummy conductors 95 a to 95 c are provided ona portion of the bottom surface of the dielectric sheet 18-2 c near theend of the dielectric sheet 18-2 c on the positive side in the y-axisdirection. More specifically, the dummy conductors 95 a, 95 b areprovided on the bottom surface of the dielectric sheet 18-2 c so as tobe arranged along the short side of the dielectric sheet 18-2 c on thepositive side in the y-axis direction. Thus, the dummy conductors 95 a,95 b overlap with the dummy conductors 92 a, 92 b when viewed in plan inthe z-axis direction. The dummy conductor 95 c is provided on a portionof the top surface of the dielectric sheet 18-2 c near the long side ofthe dielectric sheet 18-2 c on the negative side in the x-axisdirection. Thus, the dummy conductor 95 c overlaps with the dummyconductor 92 c when viewed in plan in the z-axis direction.

The connecting conductor 98 preferably has a rectangular orsubstantially rectangular shape and is provided on a portion of thebottom surface of the dielectric sheet 18-2 b near the end of thedielectric sheet 18-2 b on the positive side in the y-axis direction.The connecting conductor 99 preferably has a rectangular orsubstantially rectangular shape and is provided on a portion of thebottom surface of the dielectric sheet 18-2 c near the end of thedielectric sheet 18-2 c on the positive side in the y-axis direction.Thus, the connecting conductors 98, 99 overlap with the connectingconductor 46 when viewed in plan in the z-axis direction.

The via-hole conductors b57 to b59 pierce through the dielectric sheet18-2 d in the z-axis direction. The via-hole conductor b57 connects thedummy conductor 92 a to the dummy conductor 95 a. The via-hole conductorb58 connects the dummy conductor 92 b to the dummy conductor 95 b. Thevia-hole conductor b59 connects the dummy conductor 92 c to the dummyconductor 95 c.

The via-hole conductor b8′ pierces through the dielectric sheet 18-2 cin the z-axis direction. The via-hole conductors b7, b8, b8′ define asingle via-hole conductor and connect the external terminal 16-1 a tothe end of the signal line 20-2 on the negative side in the y-axisdirection.

In the signal line portion 10-2, the resist layer 17-2 is provided onthe bottom surface of the dielectric sheet 18-2 d so as to cover theauxiliary ground conductor 24-2. Note that, however, the connectingconductors 44, 46 and the dummy conductors 92 a to 92 c are not coveredwith the resist layer 17-2.

When the signal line portion 10-1 and the signal line portion 10-2 thathave the above-described configuration are joined together, the dummyconductor 90 a and the dummy conductor 92 a are connected together via asolder, the dummy conductor 90 b and the dummy conductor 92 b areconnected together via a solder, and the dummy conductor 90 c and thedummy conductor 92 c are connected together via a solder. Note that thesignal line portion 10-3 has a configuration of line symmetry withrespect to the signal line portion 10-2 about a line extending in they-axis direction so as to traverse the center in the x-axis direction ofthe signal line portion 10-2, and therefore, the description thereof isherein omitted. The other components of the high-frequency signal line10 h are the same as those of the high-frequency signal line 10 f, andtherefore, the description thereof is herein omitted.

According to the high-frequency signal line 10 h that has theabove-described configuration, the signal line portion 10-1 and thesignal line portion 10-2 are prevented from being easily disconnected asin the high-frequency signal line 10 f.

In the high-frequency signal line 10 h, even when the dummy conductors90 a to 90 c, 91 a to 91 c, 92 a to 92 c are provided, thecharacteristic impedance of the high-frequency signal line 10 h isunlikely to deviate from a predetermined characteristic impedance as inthe high-frequency signal line 10 f. When the high-frequency signal line10 h is connected to an antenna, variation is unlikely to occur in thecharacteristics of the antenna.

In the high-frequency signal line 10 h, the dummy conductors 90 a to 90c and the dummy conductors 93 a to 93 c are respectively connected toeach other by the via-hole conductors b51 to b53. The dummy conductors91 a to 91 c and the dummy conductors 94 a to 94 c are respectivelyconnected to each other by the via-hole conductors b54 to b56. The dummyconductors 92 a to 92 c and the dummy conductors 95 a to 95 c arerespectively connected to each other by the via-hole conductors b54 tob56. Therefore, peeling off of the dummy conductors 90 a to 90 c, 91 ato 91 c, 92 a to 92 c from the dielectric element assemblies 12-1, 12-2,12-3 of the signal line portions 10-1, 10-2, 10-3 is reliably prevented.Thus, the dielectric element assemblies 12-1, 12-2, 12-3 are joinedtogether more strongly.

Other Preferred Embodiments

The high-frequency signal line and manufacturing method thereofaccording to the present invention are not limited to various preferredembodiments of the present invention including the high-frequency signallines 10, 10 a to 10 h and manufacturing methods thereof, but can bevaried within the scope of the spirit of the present invention.

Note that the elements, features and characteristics of any of thehigh-frequency signal lines 10, 10 a to 10 h may be combined.

In the high-frequency signal lines 10, 10 a to 10 h, the connectors 100a, 100 b may not be mounted. In this case, the ends of thehigh-frequency signal lines 10, 10 a to 10 h are connected to thecircuit board preferably by soldering. Note that only one end of thehigh-frequency signal lines 10, 10 a to 10 h may be provided with theconnector 100 a mounted thereon.

The connectors 100 a, 100 b are mounted on the top surface of thehigh-frequency signal line 10, 10 a to 10 h but may be mounted on thebottom surface of the high-frequency signal line 10, 10 a to 10 h.Alternatively, the connector 100 a may be mounted on the top surface ofthe high-frequency signal line 10, 10 a to 10 h while the connector 100b is mounted on the bottom surface of the high-frequency signal line 10,10 a to 10 h.

In the high-frequency signal lines 10, 10 a to 10 c, 10 e, 10 f, 10 g,10 h, either of the reference ground conductors 22-1, 22-2 or theauxiliary ground conductors 24-1, 24-2 may not be provided. In thehigh-frequency signal line 10 d, either of the ground conductors 122-1,122-2 or the ground conductors 124-1, 124-2 may not be provided.

Note that, in the manufacturing method of the high-frequency signal line10, the signal line portions 10-1 to 10-3 are preferably formed in amatrix arrangement over the mother dielectric element assembly 112.However, the signal line portion 10-1, the signal line portion 10-2, andthe signal line portion 10-3 may be separately formed in a matrixarrangement over different mother dielectric element assemblies 112.

Note that the dielectric element assemblies 12-1 to 12-3 preferably havea linear shape, although some or all of them may have a bent shape.

Note that the high-frequency signal lines 10, 10 a to 10 h maypreferably be used as a high-frequency signal line in an RF circuitboard, such as an antenna front end module.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A high-frequency signal line comprising: a firstdielectric element assembly including a linear shape, a first end and asecond end, and a plate-shaped configuration with a first principalsurface and a second principal surface; a linear first signal lineprovided in or on the first dielectric element assembly and extendingalong the first dielectric element assembly; a first ground conductorprovided in or on the first dielectric element assembly and extendingalong the first signal line; a second dielectric element assemblyincluding a linear shape, a third end and a fourth end, and aplate-shaped configuration with a third principal surface and a fourthprincipal surface; a linear second signal line provided in or on thesecond dielectric element assembly and extending along the seconddielectric element assembly; and a second ground conductor provided inor on the second dielectric element assembly and extending along thesecond signal line; wherein a portion the second principal surface atthe first end of the first dielectric element assembly and a portion thethird principal surface at the third end of the second dielectricelement assembly are joined together such that a joint portion of thefirst dielectric element assembly and the second dielectric elementassembly includes a corner; the first signal line and the second signalline are electrically coupled together; and the first ground conductorand the second ground conductor are electrically coupled together. 2.The high-frequency signal line according to claim 1, wherein the firstdielectric element assembly includes a plurality of first dielectriclayers laminated on each other; the second dielectric element assemblyincludes a plurality of second dielectric layers laminated on eachother; the first signal line is provided in the first dielectric elementassembly; the second signal line is provided in the second dielectricelement assembly; the high-frequency signal line includes: a firstconnecting conductor provided on a portion the second principal surfaceat the first end of the first dielectric element assembly andelectrically coupled to the first signal line; and a first via-holeconductor exposed at a portion the third principal surface at the thirdend of the second dielectric element assembly and piercing through thesecond dielectric layers in a direction of the lamination, the firstvia-hole conductor being electrically coupled to the second signal line;and the first connecting conductor and the first via-hole conductor areconnected together.
 3. The high-frequency signal line according to claim1, wherein a portion the second principal surface at the first end ofthe first dielectric element assembly and a portion the third principalsurface at the third end of the second dielectric element assembly arewelded together.
 4. The high-frequency signal line according to claim 1,wherein the first signal line is provided in the first dielectricelement assembly; the second signal line is provided in the seconddielectric element assembly; the high-frequency signal line includes: afirst connecting conductor provided on a portion the second principalsurface at the first end of the first dielectric element assembly andelectrically coupled to the first signal line; and a second connectingconductor provided on a portion the third principal surface at the thirdend of the second dielectric element assembly and electrically coupledto the second signal line; and the first connecting conductor and thesecond connecting conductor are soldered together.
 5. The high-frequencysignal line according to claim 4, further comprising: a first dummyconductor provided on a portion the second principal surface at thefirst end of the first dielectric element assembly; and a second dummyconductor provided on a portion the third principal surface at the thirdend of the second dielectric element assembly; wherein the first dummyconductor and the second dummy conductor are soldered together.
 6. Thehigh-frequency signal line according to claim 5, further comprising: athird dummy conductor provided in the first dielectric element assembly;and a fifth via-hole conductor connecting the first dummy conductor tothe third dummy conductor.
 7. The high-frequency signal line accordingto claim 5, further comprising: a fourth dummy conductor provided in thesecond dielectric element assembly; and a sixth via-hole conductorconnecting the second dummy conductor to the fourth dummy conductor. 8.The high-frequency signal line according to claim 1, further comprising:a first wire conductor provided in or on the first dielectric elementassembly and the second dielectric element assembly and penetratingthrough the first signal line and the second signal line; and a secondwire conductor provided in or on the first dielectric element assemblyand the second dielectric element assembly and penetrating through thefirst ground conductor and the second ground conductor.
 9. Thehigh-frequency signal line according to claim 8, wherein each of thefirst wire conductor and the second wire conductor is bent at the firstprincipal surface of the first dielectric element assembly and at thefourth principal surface of the second dielectric element assembly suchthat the first dielectric element assembly and the second dielectricelement assembly are joined together.
 10. The high-frequency signal lineaccording to claim 8, wherein a second via-hole conductor is provided inthe first dielectric element assembly and the second dielectric elementassembly; and the first wire conductor and the second wire conductor donot penetrate through the second via-hole conductor.
 11. Thehigh-frequency signal line according to claim 1, wherein the firstdielectric element assembly includes a plurality of first dielectriclayers laminated on each other; the second dielectric element assemblyincludes a plurality of second dielectric layers laminated on eachother; the first signal line is provided in the first dielectric elementassembly; the second signal line is provided in the second dielectricelement assembly; the high-frequency signal line includes: a thirdvia-hole conductor exposed at a portion the second principal surface atthe first end of the first dielectric element assembly and piercingthrough the first dielectric layers in a direction of the lamination,the third via-hole conductor being electrically coupled to the firstsignal line; and a fourth via-hole conductor exposed at a portion thethird principal surface at the third end of the second dielectricelement assembly and piercing through the second dielectric layers inthe direction of the lamination, the fourth via-hole conductor beingelectrically coupled to the second signal line; and the third via-holeconductor and the fourth via-hole conductor are connected together. 12.The high-frequency signal line according to claim 1, wherein the firstground conductor is provided on a first principal surface side relativeto the first signal line; the second ground conductor is provided on athird principal surface side relative to the second signal line; thehigh-frequency signal line includes: a third ground conductor providedon the second principal surface side relative to the first signal linein the first dielectric element assembly and extending along the firstsignal line; and a fourth ground conductor provided on the fourthprincipal surface side relative to the second signal line in the seconddielectric element assembly and extending along the second signal line;and the first through fourth ground conductors are electrically coupledtogether.
 13. The high-frequency signal line according to claim 1,wherein the first dielectric element assembly and/or the seconddielectric element assembly has a linear shape.
 14. The high-frequencysignal line according to claim 1, wherein the first dielectric elementassembly and the second dielectric element assembly have flexibility.15. The high-frequency signal line according to claim 1, wherein aportion the second principal surface at the first end of the firstdielectric element assembly includes a step such that a thickness of thefirst end of the first dielectric element assembly is smaller than athickness of a remaining a portion the first dielectric elementassembly; and a portion the third principal surface at the third end ofthe second dielectric element assembly includes a step such that athickness of the third end of the second dielectric element assembly issmaller than a thickness of a remaining a portion the second dielectricelement assembly.
 16. A method for manufacturing a high-frequency signalline, the method comprising the steps of: forming a first signal lineportion including a first dielectric element assembly including a linearshape, a first end and a second end, and a plate-shaped configurationwith a first principal surface and a second principal surface, a linearfirst signal line provided in or on the first dielectric elementassembly and extending along the first dielectric element assembly, anda first ground conductor provided in or on the first dielectric elementassembly and extending along the first signal line; forming a secondsignal line portion including a second dielectric element assemblyincluding a linear shape, a third end and a fourth end, and having aplate-shaped configuration with a third principal surface and a fourthprincipal surface, a linear second signal line provided in or on thesecond dielectric element assembly and extending along the seconddielectric element assembly, and a second ground conductor provided inor on the second dielectric element assembly and extending along thesecond signal line; and joining together a portion the second principalsurface at the first end of the first dielectric element assembly and aportion the third principal surface at the third end of the seconddielectric element assembly such that the first signal line and thesecond signal line are electrically coupled together and the firstground conductor and the second ground conductor are electricallycoupled together and such that a joint portion of the first signal lineportion and the second signal line portion includes a corner.
 17. Themethod according to claim 16, wherein the step of forming the firstsignal line portion includes: forming the first signal line on a thirddielectric layer: forming the first ground conductor on a fourthdielectric layer; and laminating a plurality of first dielectric layersincluding the third dielectric layer and the fourth dielectric layer,thus forming the first dielectric element assembly; and the step offorming the second signal line portion includes: forming the secondsignal line on a fifth dielectric layer; forming the second groundconductor on a sixth dielectric layer; and laminating a plurality ofsecond dielectric layers including the fifth dielectric layer and thesixth dielectric layer, thus forming the second dielectric elementassembly.
 18. The method according to claim 17, wherein the first signalline portion further includes a first connecting conductor provided on aportion the second principal surface at the first end of the firstdielectric element assembly and electrically coupled to the first signalline; the second signal line portion further includes a via-holeconductor exposed at a portion the third principal surface at the thirdend of the second dielectric element assembly and piercing through thesecond dielectric layers in a direction of the lamination, the via-holeconductor being electrically coupled to the second signal line; and thestep of forming the first signal line portion further includes formingthe first connecting conductor on a seventh dielectric layer which formsthe second principal surface; the step of forming the first dielectricelement assembly includes laminating the plurality of first dielectriclayers including the third dielectric layer, the fourth dielectriclayer, and the seventh dielectric layer; the step of forming the secondsignal line portion further includes: forming a through hole penetratingthrough an eighth dielectric layer which forms the third principalsurface; and providing an electrically-conductive paste into the throughhole; the step of forming the second dielectric element assemblyincludes laminating the plurality of second dielectric layers includingthe fifth dielectric layer, the sixth dielectric layer, and the eighthdielectric layer; and the step of joining together the second principalsurface and the third principal surface includes performing a heatingprocess and a compression process on the first dielectric elementassembly and the second dielectric element assembly such that theelectrically-conductive paste solidifies, thus forming a first via-holeconductor.
 19. The method according to claim 18, wherein the step ofproviding the electrically-conductive paste is performed after the stepof forming the second dielectric element assembly.
 20. The methodaccording to claim 18, wherein the step of providing theelectrically-conductive paste is performed before the step of formingthe second dielectric element assembly; and the step of forming thesecond dielectric element assembly includes performing the heatingprocess on the second dielectric element assembly at a temperature suchthat the electrically-conductive paste does not solidify.
 21. The methodaccording to claim 18, wherein the step of joining together the secondprincipal surface and the third principal surface includes weldingtogether the second principal surface and the third principal surface.22. The method according to claim 17, wherein the first signal lineportion further includes a first connecting conductor provided on aportion the second principal surface at the first end of the firstdielectric element assembly and electrically coupled to the first signalline; the second signal line portion further includes a secondconnecting conductor provided on a portion the third principal surfaceat the third end of the second dielectric element assembly andelectrically coupled to the second signal line; the step of forming thefirst signal line portion further includes forming the first connectingconductor on a seventh dielectric layer which forms the second principalsurface; the step of forming the first dielectric element assemblyincludes laminating the plurality of first dielectric layers includingthe third dielectric layer, the fourth dielectric layer, and the seventhdielectric layer; the step of forming the second signal line portionfurther includes forming the second connecting conductor on an eighthdielectric layer which forms the third principal surface; the step offorming the second dielectric element assembly includes laminating theplurality of second dielectric layers including the fifth dielectriclayer, the sixth dielectric layer, and the eighth dielectric layer; andthe step of joining together the second principal surface and the thirdprincipal surface includes joining together the second principal surfaceand the third principal surface by soldering.
 23. The method accordingto claim 16, wherein the step of joining together the second principalsurface and the third principal surface includes: sticking a first wireconductor into the first dielectric element assembly and the seconddielectric element assembly so as to penetrate through a conductorelectrically coupled to the first signal line and a conductorelectrically coupled to the second signal line; and sticking a secondwire conductor into the first dielectric element assembly and the seconddielectric element assembly so as to penetrate through a conductorelectrically coupled to the first ground conductor and a conductorelectrically coupled to the second ground conductor.
 24. The methodaccording to claim 23, wherein the step of joining together the secondprincipal surface and the third principal surface includes sticking thefirst wire conductor and the second wire conductor into the firstdielectric element assembly and the second dielectric element assemblyso as not to penetrate through a second via-hole conductor provided inthe first dielectric element assembly and the second dielectric elementassembly.
 25. The method according to claim 16, wherein the step offorming the first signal line portion includes forming the plurality offirst signal line portions arranged over a first mother dielectricelement assembly formed by laminating a plurality of first motherdielectric layers and thereafter cutting the first mother dielectricelement assembly, thus forming the plurality of first signal lineportions; and the step of forming the second signal line portionincludes forming the plurality of second signal line portions arrangedover a second mother dielectric element assembly formed by laminating aplurality of second mother dielectric layers and thereafter cutting thesecond mother dielectric element assembly, thus forming the plurality ofsecond signal line portions.
 26. The method according to claim 16,wherein the step of forming the first signal line portion and the stepof forming the second signal line portion include forming the pluralityof first signal line portions and the plurality of second signal lineportions arranged over a first mother dielectric element assembly formedby laminating the plurality of first mother dielectric layers andthereafter cutting the first mother dielectric element assembly, thusforming the plurality of first signal line portions and the plurality ofsecond signal line portions.
 27. The method according to claim 16,wherein the first dielectric element assembly and/or the seconddielectric element assembly have a linear shape.
 28. The methodaccording to claim 16, wherein the first dielectric element assembly andthe second dielectric element assembly have flexibility.